Using copious line drawings of the 44 tree seed genera included in the ISTA “Rules for testing seeds,” to show their internal structures and how they are affected if the seeds are broken, it is demonstrated incontrovertibly that classifying pieces of tree seeds more than one-half their original size, even if they have the full quota of testa/seed coat (for that size of seed piece) as “pure seeds” is scientific nonsense. Such pieces of seeds have no potential for producing new plants. It is argued that this hiding or burying such broken seeds in the pure seed fraction in the name of speeding up the purity test is not only unethical, but is now completely unnecessary. The practice began in the very first days of seed testing, more than 80 years ago, when laboratory weighing of the purity test fractions was carried out laboriously on old-fashioned beam balances. With the advent of modern seed weighing technology in the form of rapid electronic balances, the rationale for speeding up the completion of the purity test by weighing fewer fractions, as well as including pieces of seeds in with the pure seeds, no longer has any credence, scientifically or otherwise. In fact, electronic balances permit the weighing of broken seeds separately from the other purity components in less time than it took to weigh the mixed “pure seeds” and other components on a beam balance. Proposals are made to radically alter the Rule that classifies pieces of forest tree seeds as pure seeds. Other proposals concern the provision of clear definitions of terminology used, to maintain consistency, and for proper use of italicization.
As all forest tree, shrub and other seed analysts know, when performing a purity test in accordance with the International Rules for Seed Testing (ISTA Rules), in compliance with Rule 184.108.40.206.2, if
Pieces of seed units larger than one half their original size with a portion of the testa attached are found in the working sample, they must be considered to be pure seeds.
The primary objective of this review is to demonstrate that such pieces of forest tree seeds/seed units are not merely inert, they are actually dead, particles. Whereas they may be inert by the time they find their way to the analyst’s purity table, by the time they are removed from storage for use in a tree seedling nursery they are dead. Classifying them as pure seeds has no scientific basis.
The context for the discussion that follows is found
in the second sentence of the fourth paragraph of the Introduction to the ISTA Rules (Anon. 2009) which claims that:
The test methods used must be based on scientific knowledge and the accumulated experience of those working in seed testing and quality control.
In this the word “must” is vital. And,
in the fifth sentence of the first paragraph which claims that:
The primary aim of the ISTA Rules is to provide testing methods for seeds designated for growing of crops or production of plants.
In this the words “growing” and “plants” are vital.
Abundant evidence will be documented to demonstrate that as far as Purity Test Rule 220.127.116.11.2 and forest tree seeds are concerned, these claims are patently untrue.
They are, in fact, scientifically bankrupt.
Before going into too much detail, a brief overview of the basics of the Purity Test is in order.
Rule 3.1 Object states (in part):
The object of the purity analysis is to determine:
the percentage composition by weight… and by inference the composition of the seed lot, and
the identity of the various species of seeds and inert particles constituting the sample.
Item (b) is the critical factor in this review: that is, the identity of inert particles in the sample.
To understand this correctly the ISTA definitions that follow Rule 3.1 must be considered. It is essential that the details be restated here to form the basis of the discussion that follows. Thus, Rule 3.2.1 Pure seed begins with:
The pure seed must refer to the species stated by the applicant, or found to predominate in the test, and must include all botanical varieties and cultivars of that species including:
The following structures (even if immature, undersized, shriveled, diseased or germinated, provided they can be identified as of that species) unless transformed into visible fungal sclerotia… smut balls or nematode galls:
Intact seed units (= commonly found dispersal units i.e. achenes and similar fruits, schizocarps, florets. etc.) as defined for each genus and species in the Pure Seed Definitions (PSDs) in Table 3B Part 2.
In Poaceae (Gramineae):
florets with an obvious caryopsis containing endosperm,
Pieces of seed units larger than one-half their original size.
(Sub-item 2 above is referred to throughout the following text as Rule 18.104.22.168.2)
Rule 22.214.171.124.2, as was pointed out by Ashton (2000), does not define how to measure “one-half.” Does it mean that only the length of the seed is to be considered, or all of its dimensions, i.e. seed mass (see also Gorian et al. 2006). It was contended that for symmetrically-shaped seeds an estimate based on a linear measurement should be considered. For asymmetrical seeds it may be necessary to consider more than one dimension. However, actual measurements do not necessarily give a more accurate result because the appearance of the missing fragment can only be estimated. By way of confirmation, Ashton (2000) reminded everyone that seeds that are “exactly one half their original size are classified as inert matter” (Rule 126.96.36.199).
In this review only the length of the seed will be considered, even though—as will be illustrated—forest tree seeds are usually asymmetrical.
The Rules continue with:
From the above main principles, exceptions are made for certain genera of Poaceae (Gramineae) (Table 3B, Part 2): … (details omitted as they are unimportant herein).
Rule 3.2.2 Other seeds (mentioned here for the sake of completeness, to be considered later)… shall include seed units of any plant species other than that of pure seed…
Then comes the really important part:
Rule 3.2.3 Inert Matter
Inert matter shall include seed units and all other matter and structures not defined as pure seed or other seed as follows:
Seed units in which it is readily apparent that no true seed is present. Does this not apply to shriveled, diseased, pre-germinated seeds, or broken seeds of any size?
Florets of those species listed in 188.8.131.52 with a caryopsis less than the minimum size. (Remaining details not important for forest tree seeds.)
Pieces of broken or damaged seed units half or less than half of the original size.
Those appendages not classed as being part of the pure seed in the pure seed definitions for the species (Table 3B Part 2). Appendages not mentioned in the pure seed definitions must be removed and included in the inert matter. (This would apply to seed wings of certain gymnospermous species—see item 7 below.)
Seeds of… Cupressaceae, Fabaceae (Leguminosae), Pinaceae, Taxaceae, and Taxodiaceae with the seed coat entirely removed. In Fabaceae (Leguminosae), separated cotyledons are regarded as inert matter, irrespective of whether or not the radicle-plumule axis and/or more than half of the testa may be attached.
Seeds of Cuscuta spp. … (other details not important herein.)
Unattached sterile florets, empty glumes, lemmas, paleas, chaff, stems, leaves, cone scales, wings, bark, flowers, nematode galls, fungus bodies… smut balls, soil, sand, stones, and all other non seed matter.
All material left in the light fraction… (other details not important herein).
Attention is drawn to Rule 184.108.40.206 (item 5 above) which states that “in Fabaceae (Leguminosae), separated cotyledons are regarded as inert matter, irrespective of whether or not the radicle-plumule axis and/or more than half the testa may be attached.”
No mention is made of separated cotyledons in the Cupressaceae, Pinaceae, Taxaceae or Taxodiaceae. Clearly, the Fabaceae (Leguminosae) have been given special treatment.
Perhaps this is because the Cupressaceae, Pinaceae, Taxaceae and Taxodiaceae (and the Berberidaceae and Brassicaceae [Cruciferae]) were “shoe-horned” into Rule 220.127.116.11 well after this Rule had been written, and no-one gave the slightest consideration to their requirements. This will become a major issue in discussing gymnospermous and angiospermous tree seeds.
Why is this? Why do only some of the Fabaceae (Leguminosae), which includes the forest trees Acacia, Gleditsia, Robinia, Sophora (see Table 1), receive special attention, but not other forest tree seeds?
Probably because forest tree seeds were not recognized, i.e. were not included in the Rules until the late 1950s/early 1960s.
Also, there is no further reference to the radicle-plumule axis with more (or less) than half the testa still attached, so it has to be assumed that this part—the radicle-plumule axis—of the seed is also to be classified as “inert matter.”
Should this not be made completely clear?
This is obviously a lack-a-daisical approach to this issue, and it has never been thought through scientifically.
Based upon the preceding General Overview, what actually comprises a Purity Test in non-ISTA language forms the basis of this review. As all purity analysts know, it is a visual examination (a rapid visual examination, speed is so important—to be discussed in PART II) of the external appearance of the particles in the sample. As will be demonstrated, pieces of broken tree seeds of any size are easily recognizable and, because they have zero potential for producing a new plant, they must be classified accordingly: not “pure seed.”
However, does this mean that the analyst is being asked to perform a growth assessment? No, the analyst is being asked to recognize that pieces of broken tree seeds of any size have no more potential for producing new plants than do unattached sterile florets, empty glumes, chaff, smut balls, etc. (see item 7 above) and so should classify such pieces as “inert matter,” if not as “dead matter” (see following).
So what is really meant by “pure seed?”
The word “pure” can be defined in several different contexts (see Dictionary quotes). However, the use of “pure” by ISTA has never been defined in relation to seeds, despite the many Pure Seed Definitions.
In the Glossary at the end of this review are several definitions of the word “pure” quoted from well-known English Language Dictionaries. Prominent among these are the definitions “uncorrupted; faultless; genuine article; free from alteration; free from anything debasing or deteriorating; unadulterated.” (See especially Grove 1961, and Murray 1971).
“Unadulterated” is a significant word in this context. According to the Concise Oxford Dictionary of Current English (Fowler and Fowler 1964), it means the opposite of “adulterated” which, in turn, means “spurious,” or “counterfeit.”
Being the international agency for testing and certifying seed quality, ISTA can define a “pure seed” in any manner it pleases. Since the Rules were first promulgated, ISTA has drawn up (concocted might be a better term) 63 Pure Seed Definitions (PSDs) (Rules, Table 3B Part 2). To the non-analyst lay-person, such as the forester, even the farmer, anyone who is a seed user, the term “pure seed” connotates, i.e. suggests, that the seed(s) in question might produce new plant(s). Of course, the purity analyst cannot determine if the seed(s) will germinate because (as already noted) the purity test is not a growth test. Nevertheless, some unbroken, i.e., intact, seeds may be devoid of an embryo and associated tissues (empty seeds), or may contain an insect larva, but this cannot be determined by the purity analyst and so they may appear superficially to be sound, that is “pure seeds.” Conversely, as already claimed in the foregoing, the analyst should recognize that broken tree seeds are (so-called) “inert matter.”
The heart of this review is aimed at showing that if some forest tree seeds are broken into pieces of any size, including those “more than one-half their original size,” these cannot be regarded as “pure seeds” according to the dictionary definitions in the Glossary because they are not “free from alteration” (Grove 1961), they have been adulterated. That is, they are “not unadulterated,” they are “spurious.” At the expense of repetition, such pieces of forest tree seeds do not require any growth tests to be visually and rapidly recognized for what they are, viz. not “pure seeds” but so-called “inert matter.” Actually, as will be reasoned below, they are dead matter.
Indeed, the analyst is required to recognize them and to judge if they meet the “more than one-half their original size” criterion (Rule 18.104.22.168.2). The scientific knowledge referred to in the Introduction to the Rules, and upon which test methods must be based, will be documented in the following pages to establish, beyond any doubt, that for forest tree seeds such “pieces of seeds,” larger (or smaller) than one-half their original size, have absolutely no potential for producing new plants. They have no more value to the forester, the silviculturist, and any other seed user, than the “chaff, stems, cone scales, wings, bark, flowers, nematode galls, fungus bodies… smut balls, soil, sand, stones” listed in Rule 22.214.171.124, and should not be classified as “pure seed,” but as “inert matter.” Or, as mentioned above, even Dead Matter.
So what is meant by “inert matter?”
Inert matter applies to anything that has no life functions, such as broken seeds.
Also in the Glossary are several definitions of the word “inert” quoted from well-known English Language dictionaries. Most speak of the “lack of power to move,” but do not state that this “lack of power” is permanent. Two definitions (Grove 1961, Stein and Urdang 1967) do include the word dead, or lifeless, so it becomes a matter of context in which the word is applied. In a human context for example, a person may fall down and lie “inert,” that is, “without power to move or act” until medical help arrives. The person is revived and recovers the power to move.
Even intact, fully-developed forest tree seeds are “without power to move or act,” that is, they are inert when they are dormant, which is all of the time they are in storage until they are appropriately prepared for sowing in a nursery to produce reforestation stock: that is, until they are revived for germination. In other words, dormant seeds do not move, they do not grow because the power to move or act is not available in their dormant state, and they remain in this state for months, to several years (Bonner 2008).
Thus, based on official English-language definitions, an intact, fully developed, mature, dormant Douglas-fir (Fig. 1) (or Scots/Swedish pine, or Sitka spruce, etc.) seed would be classifiable as both “pure seed” and “inert matter.” That is, an “inert,” pure seed.
Seeds of a Protoaceae (Leucospermum spp.) and two legumes (Liparia spp. and Acacia spp.) collected in 1802–03 were germinated 150 years later at the Royal Botanic Gardens, Kew, United Kingdom. Supported by carbon-dating, other seeds have survived over 200 years (Daws et al. 2007), likely because they remained intact.
That is to say, these seeds remained “inert” this length of time (200 years), but they did not perish. Until they were ready to germinate, by having been subjected to the correct pre-germination treatment, they remained “inert.” That is, they did not move, they did not grow. But they were not dead as a tetrazolium test (Rule 6) would have quickly determined.
To press the issue of dormant-inert-not dead (likely intact) further, it is of value to note that seeds of a non-tree member of the Fabaceae (Leguminosae), the genus Lupinus (included in the Rules), were unearthed in 1954, kept in a bottle for 12 years before being sent to the National Museum of Canada where they were carbon-dated as being between 10,000 and 15,000 years old. Several were placed on damp filter paper and germinated within 48 hours. These seeds were some 8,000 years older than the then oldest-known seeds, those of the sacred lotus, that germinated after lying dormant (inert-not dead) in a far-Eastern peat bog (Porsild 1967).
Before pursuing this further, consider the following analogies:
A jeweler cuts a rough diamond into two pieces—one is larger than one-half the original size (to be used as a pendant), while the other piece is smaller than one-half the original size (to be used in a ring). Both pieces remain pure diamond. The original size is in no doubt.
A forester plucks a needle from a pine tree, breaks it into two pieces—one piece being larger than one-half the original size, while the other piece is smaller than one-half the original size. Both pieces remain pure pine needle. Again, the original size is in no doubt.
A farmer randomly removes a seed potato from a storage bin to check its condition. Satisfied after hacking it into two unequal pieces he throws them back into the bin. The larger piece was larger than one-half the original size, while the other piece is smaller than one-half the original size. Both pieces remain pure seed potato. The original size is in no doubt.
Why, then, does ISTA insist that when a seed is broken into two pieces, only the piece larger than one-half the original size is to be regarded as “pure seed,” while the other piece (smaller than one-half the original size) is not to be regarded as “pure seed?” Are not both pieces of the seed organically still “pure seed” using the diamond, pine needle and oak leaf analogy? In any case, unless all the seeds in the seedlot are very uniform in size, how can the analyst be sure of the original size?
There is a difference, of course, between the diamond, pine needle, seed potato and the seed. The diamond has always been inanimate (see Stein and Urdang 1967; Cayne and Lechner 1987 in the Glossary), whereas the pine needle was animate until plucked from its “mother trees,” at which time it became inanimate, that is it is en route to becoming dead. The seed potato remains animate unless it goes mouldy. Likewise, a forest tree seed (or any other type) containing a germ is a living, animate, breathing (=respiring) entity. Its outer cover, the seed coat or testa, protects the tissues that will give rise to a new plant under the proper conditions. Damaging this cover, that is adulterating—even cracking—it, exposes the internal tissues to (a) disease, and/or (b) excess drying when the seeds are prepared for storage (more on this below). The diamond is not subjected to these stresses; while the pine needle eventually crumbles and dies, as does the seed potato if not planted soon. Likewise, pieces of broken seeds.
In the previous analogy, the diamond—piece of or complete—is not merely “inert,” nor is it dead since it never had any living properties. It always rested in peace, it had no mortal coil to shake off because it was always inanimate. But it remains “pure” diamond.
Therefore, it must be asked if ISTA (and other seed testing agencies such as AOSA—the Association of Official Seed Analysts of North America) is using the correct term to describe forest tree seed units from which the seed coats have been entirely removed as “inert matter” (Rule 126.96.36.199). As will be discussed in detail below, these seed units are not merely “inert” as defined above. They are dead.
Again, any doubts on this can be quickly assuaged with a tetrazolium test (Rule 6). They are as DEAD as any chaff, stems, leaves, cone scales, wings bark, soil particles, sand, stones (as stipulated in Rule 188.8.131.52). But soil particles, sand, stones are not dead. They never had any life, so they cannot be dead or, by definition “inert.” They should be referred to more correctly as inanimate.
Why not simply call such seeds “impurities?”
Because ISTA has chosen, inadvertently over the past 80 years, to play games with basic definitions.
It is probable that it will be argued (“an exchange of ignorance”—see below) that the words inert, dead and inanimate are one and the same. However, the main issue remains:
How can dead seeds be “pure seeds?” That is, seeds known to the analyst to be dead based on scientific knowledge and experience?
Because ISTA has failed to recognize them as such, choosing to confuse the result of the Purity Analysis.
Table 1 lists the 19 PSDs that apply to the 21 families (44 genera) of forest trees to which the Rules apply. All PSDs (11, 47, 49, 50, 51) for the 17 gymnospermous genera state that pieces of seed units larger than one-half of their original size (Rule 184.108.40.206.2) are to be considered as “pure seed,” provided a portion of the testa remains attached. No explanation is given as to whether this must be a small or large portion of the testa.
Piece of Seed (POS)
POS with testa
Picea, Pinus II
POS with testa
Calocedrus, Chamaecyparis, Cupressus, Thuja Cryptomeria, Sequoia, Sequoiadendron
POS with testa
POS with testa
Abies, Cedrus, Larix, Pinus I, Pseudotsuga, Tsuga
POS with testa
Piece of Seed (POS)
POS with or without testa
POS with testa
POS with/without testa (part of or none)
POS with testa
POS with/without pericarp/testa (part of or none)
POS with testa
Aceraceae, Magnoliaceae, Oleaceae, Simaroubaceae, Ulmaceae
Acer, Liriodendron, Fraxinus, Ailanthus, Ulmus
POS with/without pericarp/testa (part of or none)
POS with/without pericarp/testa (part of or none)
POS with/without testa
POS with/without pericarp/testa (part of or none)
POS with/without pericarp/testa (part of or none)
Betulaceae, Fagaceae, Tiliaceae
Carpinus, Corylus, Castanea, Fagus, Quercus, Tilia
POS with/without pericarp/testa (part of or none)
POS with/without pericarp/testa (part of or none)
POS with/without testa
Eleven of the 14 PSDs (10, 11, 12, 20, 48, 50, 52, 53, 54, 55, 56, 57, 58, 60) to which the 28 angiospermous genera are assigned, allow that pieces of seed units more than one-half their original size are to be recognized as “pure seed” even if no pericarp or testa remains attached. That is, completely naked seeds are to be recognized as “pure seed” provided they are larger than one-half of their original size. This is hair-splitting at its finest.
It should be clear from this that the ISTA idea of “pure seed” differs entirely from that of seed users—the farmer, the forester, the horticulturist.
A more complete history of the Rules will be presented in Part II, but it is useful to mention here that the early Rules (roughly 80 years ago) were formulated to deal with the quality of agricultural crop seeds. Forest tree seeds were not introduced into the Rules until some 50 years ago (in 1956?). The precise date of this introduction is uncertain as this review is written, but it is known that tree seeds were included in the Rules by 1961 when this reviewer underwent basic training at the ISTA-Accredited Seed Testing Laboratory of the United Kingdom’s Forestry Commission, Alice Holt Lodge Forest Research Station (see Reviewer’s Credentials at the end of this review). It is probably safe to say that the provision for Pieces (or Piece) of seed (or seed units) of non-tree species that were larger than one-half the original size as pure seeds was already contained in the 10 PSDs to which some tree seeds were assigned. For the bulk of other forest tree seed genera 9 new PSDs had to be written. Each and every one of these PSDs contains Rule 220.127.116.11.2. That is to say, although certain tree seed genera were shoe-horned into existing definitions, all tree seeds were expected to comply with the existing piece/pieces provision without exception. That is, no consideration was given to the scientific knowledge of forest tree seeds.
In contrast, it must be noted that special provisions had already been made for certain Poaceae (Gramineae) genera and these provisions exist today as Rule 18.104.22.168.1. So why do some genera in the Poaceae receive special attention, but not tree genera in the Cupressaceae, some Fabaceae, Pinaceae, Taxaceae and Taxodiaceae? Why has ISTA persevered in its studious avoidance of forest tree seed biology, the science of which is abundantly documented and which clearly points to any piece of tree seed as being no more valuable to the forester for producing a new plant than a similarly-sized piece of rock, needle, cone scale, or twig?
It is probably true that other tree seed scientists have asked these or similar questions in the past.
The Discussion that follows is divided into to two main parts, followed by a Literature Cited list, the Reviewer’s qualifications, and three Appendices, two of which include the bulk of the illustrations, and a Glossary.
Part I addresses the structure of forest tree seeds, and how these structures are impacted when the seeds are broken into pieces. Aspects of tree seed biology that demonstrate that broken forest tree seeds have zero use for the production of new plants will be included to further demonstrate that they must not be given the connotation of “pure seeds.”
Part II comprises a more inclusive historical overview of the purity test to show, among other things, how it existed in the first published Rules, how and when it was modified, and who promoted the changes. This will provide an opportunity to raise some ethical questions.
Except for Sequoiadendron, for which there are no illustrations, the remaining 16 of the gymnospermous genera included in the Rules, viz. Abies, Calocedrus (formerly Libocedrus), Cedrus, Chamaecyparis, Cryptomeria, Cupressus, Juniperus, Larix, Picea, Pinus, Pseudotsuga, Sequoia, Taxodium, Taxus, Thuja, and Tsuga will be discussed first, followed by 25 angiospermous genera, viz. Acacia, Acer, Aesculus, Ailanthus, Alnus, Betula, Carpinus, Castanea, Cornus, Corylus, Eucalyptus, Fagus, Fraxinus, Ginkgo, Gleditsia, Ilex, Liriodendron, Platanus, Populus, Quercus, Robinia, Salix, Sophora, Tilia, and Ulmus.
A tropical forest tree seed genus (Tectona–teak) will be included also.
Except for two photographs (Figures 1 and 2) in Part I, all seed structures will be illustrated by the excellent line drawings published in “Seeds of Woody Plants in the United States” (Schopmeyer 1974), used with permission. Many of these drawings were published in the first “Woody-Plant Seed Manual,” USDA Misc. Publ. 654 (Anon. 1948), and have been reused—and added to—in the recent “The Woody Plant Seed Manual” (Bonner et al. 2008) for which this reviewer was privileged to revise the Abies (fir) chapter. The early original drawings (Anon. 1948) were made by several artists, including Leta Hughey, W.H. Lindemann, A. Kuban, N.T. Mirov, and Helen M. Dille. The added genera in Schopmeyer (1974) were drawn mainly by Suzanne Foster Manley. Such drawings were also used in Young and Young (1992), which was published as a revision of Schopmeyer (1974).
For purposes of this review, the line drawings have been modified, using Photoshop, by adding check marks to the vertical scale to show proportional seed lengths of 25%, 50%, and 75% of the overall size from either the chalazal (cotyledonary) or micropylar end. To indicate what happens when seeds are broken, portions of the line drawings have been erased and a broken (dashed) line added to indicate the position of each inferred break at the relative positions along the length of the seed. In all other aspects the drawings remain unaltered. Part II will include a few additional photographs taken by the reviewer, plus others provided by the Royal BC (British Columbia) Museum.
As is demonstrated in all the illustrations (Figs. 3–28 in the text and Appendix I), with the exception of Taxus (yew) (Figs. 23–28), all gymnospermous seeds possess the same basic internal structures: an almost linear embryo (2n-diploid) that occupies, at seed maturity, 75% or more of the length of the cavity within the female megagametophyte (1n-haploid) tissue, surrounded completely by an intact seedcoat/testa (1n). Thus, (except for Taxus) the mature embryo is almost the full external-length of the seed.
Internal structures are shown to full advantage in Figure 1, a photograph of the sagittal half of a mature Douglas-fir (Pseudotsuga menziesii) seed. The embryonic cotyledons can be seen; at their base is the apical meristem from which the new shoot will form. The root meristem, from which the seedling radicle develops, is surrounded by its protective root cap of parenchymatous tissue.
Figure 2 is a similar photograph, again of a Douglas-fir seed, but with an immature, developing embryo, although the megagametophyte tissue is fully developed. It can be seen clearly that the cavity within the megagametophyte tissue is already fully formed, that is, the embryo does not have to “force” its way through this tissue as it elongates. The megagametophyte tissue contains the energy for the growing embryo; this energy is absorbed by the embryo via the cotyledons (Edwards 1969).
Because they possess the same basic internal structures, what happens to these structures when the seeds are damaged will be discussed in full detail for two genera, viz., Larix (Pinaceae) and Thuja (Cupressaceae). These two genera have been selected because the available illustrations provide not only an internal impression, as if by x-ray, but also an exterior, adaxial view of the complete seed, which represents the view that the purity analyst would have.
The internal morphology of Taxus (yew) is different and a separate discussion will be required. All other Gymnospermous species are illustrated in Appendix I.
(or, as Monty Python’s Flying Circus described it, “Number 13: the Larch”!)
Although the larch seed illustrated in Figures 3–11 is a North American species (Larix laricina), analysts familiar with this genus will know that all larch seeds are easily recognizable as such. A small seed at 3.5 mm in length, L. laricina retains a remnant of the seed wing that, as in Douglas-fir (Pseudotsuga), is fused to the seed coat (PSD51) (Fig. 3).
This means that when these seeds are processed after extraction from the cones in which they developed the wing has to be broken off, a likely source of seed damage. As already mentioned, on the vertical axis to the left in all the figures are check marks showing 25%, 50% and 75% of the seed length, from either end of the seed. Thus, when a piece of a broken seed is considered (as in Fig. 4), the size of the piece can be readily assessed.
The piece of seed shown in Fig. 4 is approximately 55% of the original length as measured from the chalazal (cotyledon) end of the seed. Thus, it is larger than one-half the original size, so an analyst must classify it as a “pure seed.” The view of the internal structures (on the left) shows it has lost its embryonic root meristem from which the radicle would develop. It should be clear that this piece of seed more than one-half the original size, with a full compliment of seed coat (or testa) attached, represents the same situation—separated cotyledons—for which seeds of the Fabaceae (Leguminosae) would be classified as “inert matter.” But only seeds of the Fabaceae (Leguminosae), not seeds of Cupressaceae, Pinaceae, Taxaceae or Taxodiaceae. Why? Something appears to be amiss here.
Even if this piece of seed was sown, or included in a germination test, it would be impossible to form a primary root. Because all gymnospermous seeds exhibit epigeal germination, this seed has zero possibility of producing a new plant. Yet, even though it is easily recognizable to the purity analyst for what it is, as is clear in the drawing of the external (adaxial) view of the seed, it must be classified as a “pure seed” according to Rule 22.214.171.124.2. If a tetrazolium test (Rule 6) was performed on such a seed, how would the staining pattern (if staining occurred) be interpreted for an incomplete embryo?
In similar fashion, Fig. 5 shows a piece of a larch seed approximately 55% of the original as measured from the micropylar end. That is, it is larger than one-half the original size so the analyst must classify it as a “pure seed.” The internal view on the left shows that it lacks the embryonic cotyledons and the apical meristem. Were it to be sown, or included in a germination test, the remnant of the embryo probably would swell and the broken surface would extrude beyond the megagametophyte surface. Because there is no chalazal end to the seed the elongating embryo remnant would meet no resistance and would not emerge via the micropyle (epigeal germination).
Even if the radicle were to penetrate the micropyle, the lack of cotyledons means that this seed is doomed. The cotyledons are the organs that absorb the energy (mainly sugars) for growth from the megagametophyte (Edwards 1969), and their absence means the seed will be unable to grow. Yet it must be classified as a pure seed according to Rule 126.96.36.199.2. If a tetrazolium test (Rule 6) was performed on such a piece of seed, how would the staining pattern—if any staining occurred—be interpreted for an incomplete embryo?
A critical comparison must be made between the larger piece (more than one-half the original size, so “pure seed”) that is shown in Fig. 4 with the smaller piece (less than one half of the original, so “inert matter”) that was broken off when the piece of seed shown in Fig. 5 was formed. These two pieces are shown side by side in Fig. 6.
Likewise, Fig. 7 shows side by side the larger piece (more than one-half the original size, so “pure seed”) shown earlier in Fig. 5 with the smaller piece (less than one half of the original, so “inert matter”) that was broken off when the piece of seed shown in Fig. 4 was formed.
What is the difference between these pairs of pieces of seeds? The only difference is an arbitrary, small variation in size. In each case, one piece is 55% of the original size, and must be classified as a “pure seed,” while the other is 45% of the original size and is to be considered “inert matter.” Yet neither have any potential for producing a new plant.
What scientific principle is being invoked to distinguish them from one another? In other words, why are both pieces (larger and smaller) not considered being “pure seed” or, conversely, not “inert matter?”
No scientific principle, merely an arbitrary difference in size.
From the discussion presented so far, it should be clear that no scientific principle is at work. That the distinction is pure unadulterated rubbish.
Rule 188.8.131.52.2 assumes that the analyst knows the original size of the seed. This, in itself, appears to be a contradiction, since the seed has been broken and a piece is missing. As already noted, this Rule was introduced well before forest tree seeds were included in the Rules, being designed primarily with crop seeds in mind. Because they are highly bred, crop seeds are likely to be quite uniform in all aspects, including size. Thus, it is probably quite easy for the crop seed purity analyst to judge that this piece of seed is larger or smaller than one-half of the original size, because all seeds in that working sample look alike. However, see Ashton (2000).
For the vast majority of tree seeds, even those produced in forest tree seed orchards, seed size is far from uniform. Experience with noble fir (Abies procera in North America, a.k.a. A. nobilis in Europe) showed that seed size varies from mother tree to mother tree, from one aspect of the crown to another (in the northern hemisphere, seeds developing on the south aspect of the crown tend to be larger), from cone to cone on the same branch, within a single cone (seeds near the cone extremities are usually much smaller than those in the cone’s centre), and even between the two seeds borne on a single ovuliferous scale (Edwards 1969). In Sitka spruce (Picea sitchensis) seed size is known to affect seedling attributes (Chaisurisri et al. 1994).
As all tree seed producers/processors are aware, this variation in seed size must be considered when the seedlot is cleaned, especially if an aspirator cleaning system (air is drawn through the seed mass) is used to lift lighter particles such as needles, cone scale fragment, empty seeds, etc. from the heavier ones. This is a modern, mechanized method of winnowing. For such a system to be efficient, that is, to avoid small filled seeds from being removed along with large empty seeds, the seedlot first must be sized.
For gymnospermous seeds this is usually done by passing the seedlot (after wing removal) over a series of vibrating, inclined screens. Three, sometimes four, different mesh sizes are used; the largest seeds are retained on the upper screen, the medium-sized seeds retained on the screen below, and the smallest seeds falling through to the lowest screen through which any dust or other very fine debris falls onto a conveyor belt for disposal. Each size class is then cleaned separately in the aspirator cleaner. Air speed is adjusted so that light, empty seeds for that size component can be drawn off for disposal leaving the heavier filled seeds. Seeds containing an insect larva may also be removed at this time. If there were any broken seeds to begin with most, if not all, may have been removed as debris. But there is no guarantee that the seedlot is free of all pieces of seeds.
When each size component has been satisfactorily cleaned, all the filled seeds from each size component are then thoroughly remixed. This is a vital step in retaining the genetic integrity of the seedlot. However, because such sizing is an integral part of tree seed processing, application of Rule 184.108.40.206.2 to tree seeds makes no sense whatsoever.
While other methods of cleaning may be used, it must be recognized that seed size varies within any and all seedlots. The degree of variation differs among species, and from seedlot to seedlot within a species, but the purity analyst must apply the Rules, particularly Rule 220.127.116.11.2 uniformly. For a working sample from a seedlot with even a modest degree of variation in seed size, it is difficult if not impossible for the analyst to correctly judge whether a “piece of seed” is “larger than one half the original size” because the “original” seed is not available to make a correct decision. There are other reasons, already alluded to, for not classifying “pieces of seeds” as pure seed and these will be discussed more fully below.
As an example of actual variation in seed size, or more correctly seed mass (compare with Ashton 2000), Fig. 8 is included here courtesy of Dr. F. Gorian (Italy). In his presentation at the 2006 ISTA Forest Tree and Shrub Seed Committee (FTSSC) Seminar in Verona, Dr. Gorian showed that, across its natural range, seed mass in Larix decidua (European larch) may vary by up to 250%. Suppose the purity analyst is given a working sample from a range-wide collection of European larch (Mother Nature forbid that seeds from across the range should be mixed into one seedlot. This is highly unlikely given today’s knowledge concerning matching seed collection with planting site). How would the analyst know if a piece of seed similar to that shown in Fig. 4 or Fig. 5 is a small piece (smaller than one-half the original size) from a large seed (P4 in Fig. 8), and therefore “inert matter,” or a large piece (larger than one-half the original size from a small seed (P1 in Fig. 8), and therefore a “pure seed?” As will be discussed in Part II, the analyst is not supposed to stop and consider such matters. And if one analyst does so, the next analyst might not agree (again, see Ashton 2000). This is but one example to illustrate how nonsensical Rule 18.104.22.168.2 is for forest tree seeds.
Critics might regard a piece of seed that is 55% of the length of the original is borderline for Rule 22.214.171.124.2. (but see Ashton 2000) and, even though it meets the “larger than one-half the original size” criterion, larger pieces should be considered. So what happens to the internal structures if the larch seed shown in Fig. 3 was broken so that a piece close to 75% of the original size measured from the chalazal end is encountered? This is illustrated in Fig. 9 showing a piece of seed that contains almost a complete embryo, only the tip of the embryonic radicle, perhaps only part of the root cap is missing; typically, the root meristem does not extend to the tip of the root cap. So if sown, or included in a germination test, a germinant might be seen, even a normal-looking one. However, the megagametophyte tissue has been exposed so unless this seed is used—sown or germinated—fairly soon it will perish in storage. More on tissue exposure later.
Likewise, Fig. 10 shows a piece of seed measuring 75% of the original size from the micropylar end; this piece also contains an almost complete embryo, only the tips of the cotyledons have been lost. However, the megagametophyte tissue at the chalazal end is exposed, so unless this seed is used—sown or germinated—fairly soon it will perish in storage. Even if it does germinate the embryo will elongate via the chalazal end, not via the micropyle, because there is no resistance to encourage the radicle to emerge via the micropyle (epigeal germination). This means that the cotyledons will lose contact with the megagametophyte tissue, the embryo’s source of energy, and it will cease to grow. Its usefulness for producing a new plant is completely compromised therefore.
What if the seed is merely chipped, at either end, so that the piece measures 90% or more of the original? Fig. 11 shows just such a seed with just enough of the seedcoat missing to expose the megagametophyte tissue at the micropylar end. To the uninitiated this might appear to be a piece of seed that could give rise to a new plant, so it is worthy of the connotation “pure seed.” However, since the megagametophyte tissue is exposed, this piece of seed has little to no chance of producing a new plant should it undergo dry, cold storage.
Fig. 12 illustrates a piece of seed with just enough of the seedcoat missing to expose the megagametophyte tissue at the chalazal/cotyledon end. If used promptly after it was discovered, it might germinate, with the embryo exiting via the chalazal end. But the cotyledons will soon lose contact with the megagametophyte tissue after which growth will cease. In a germination test this would produce an abnormal germinant—cotyledons exiting first. Because of this, such a piece of seed has no usefulness in producing a new plant. If placed in storage, this piece of seed will perish.
Why must either of these pieces be classified as “pure seed?”
Because ISTA is not applying the scientific principles involved.
The Rules state that even if a larch seed is broken at 75%, or even 90%, of its original size it must be recognized as “pure seed.” This is because the Rules are not conversant with tree seed biology.
Incidentally, chipping Abies procera seeds at the micropylar end and then soaking them for 24 hours prior to sowing in a nursery flat has the same effect as 3–4 weeks of pre-chilling (Edwards 1969).
While seed breakage is more likely across the length of any gymnospermous seed, other damage may occur. For example, the seed may be broken along its length, as shown in Fig. 13. In this example the embryo remains completely intact, but the megagametophyte tissue is exposed along the damaged edge. Should this seed be used—sown or germinated—relatively soon after it is discovered, a normal germinant may be forthcoming, although it is possible that the elongating embryo will bend and force its way sideways from the surrounding tissues, with the radicle not exiting via the micropyle. Its usefulness for producing a new plant is highly questionable therefore. If stored, as in other examples above, exposure of the megagametophyte tissue will cause this piece of seed to perish.
Sometimes the seed coat may be merely cracked, as shown in Fig. 14. Although having the appearance of an otherwise intact seed to the purity analyst, exposure of the megagametophyte tissue means that this seed, essentially 100% of the original, is likely to perish if placed in cold, dry storage.
All of the issues presented above apply equally well to seeds of all other members of the Pinaceae (Abies, Cedrus, Picea, Pinus, Pseudotsuga and Tsuga), illustrations for which are found in Appendix I.
One more seed type, a member of the Cupressaceae, (Thuja occidentalis, northern white cedar), will be discussed in detail for a few additional reasons. As with the larch seed, the line drawings available for this species offer both an external adaxial view of an intact seed and the x-ray-type of view showing the internal structures. Some additional notes will be included for other genera.
While seeds of all genera in the Cupressaceae presented here are similar to the Pinaceae in their internal structures, in that their embryos are linear and occupy the bulk of the seed length, Calocedrus, Chamaecyparis and Thuja add a new twist to the discussion, viz., seeds of these three genera bear two wings that are not removed in routine processing because doing so is known to cause damage. For this reason damaged seeds may be less frequent. However, they need to be discussed in some detail in regard to Rule 126.96.36.199.2.
Similar to the illustrations for Larix, line drawings are available (Schopmeyer 1974) for Thuja occidentalis that offer both an external adaxial view that the analyst would have of an intact seed, plus the x-ray-type of view showing the internal structures. Illustrations for pieces of seed 51–55% of the original size, as well as for larger pieces, 75% and 90% are shown.
For Thuja occidentalis, northern white-cedar, the intact seed as viewed from its adaxial surface is shown at left in Fig. 15, with the “x-ray” view at right. Because the seed coat is fairly soft and easily damaged, the two wings are not routinely removed in seed processing. By now it should be clear what occurs if seeds of this species are broken, either into pieces that are more than one-half their original size, and to be regarded as “pure seeds” (Rule 188.8.131.52.2), whether 51–55% of the original from the chalazal end (Fig. 16) or from the micropylar end (Fig. 17). It should be obvious also what happens to the internal structures if the Thuja seed is broken at approximately 75% (Figs. 18 and 19) or even 90% (Figs. 20 and 21), from either end. A Thuja seed broken lengthwise down one side is shown in Fig. 22. Once again, because of the need to store surplus seeds the lifespan of broken specimens can be expected to be very short.
The following are some brief additional notes on Calocedrus, Chamaecyparis, Cupressus, Ginkgo and Juniperus. Illustrations for these genera can be found in Appendix I.
Although appearing to have only one wing, each Calocedrus decurrens seed actually has two: a longer, wide wing that extends lengthwise beyond the seed on one side, and a narrower, much shorter one just emerging alongside the first from the opposite side (Appendix I). Both wings are persistent and project past the narrow micropylar (radicle) end of the seed rather than the chalazal (cotyledon) end as in most other conifers. During germination the radicle emerges from the narrow, winged end of the seed. How the internal morphology of an intact seed is impacted if it is broken into a piece 55% or more of the original size (as measured from either end) is also shown in Appendix I. The same concerns apply as for the larch and arborvitae seeds even if the seeds are broken into larger pieces.
Like those of Thuja, seeds of Chamaecyparis lawsoniana, Port-Orford cedar, bear two wings, one on either side of the seed as seen from an adaxial view (Appendix I). Again, these are not routinely removed in seed processing because the seed coat is fairly soft and the seed easily damaged. Broken seeds may be infrequent, therefore, but should damage occur the same concerns as for Larix and Thuja apply.
Cypress seeds vary widely in shape and size (2–8mm long), those of Cupressus arizonica var. arizonica shown in Appendix I being among the smallest. In general, they bear either a minute wing (a tegumentary extension of the seed coat) or none at all, making dewinging unnecessary. For these reasons cypress seeds are unlikely to be subject to the same damage as those of the Pinaceae. However, their embryos are linear and occupy the bulk of the seed length, so if damage does occur why should pieces of Arizona cypress seeds of any size be classed as pure seeds?
The fleshy cones of Juniperus scopulorum, usually referred to as berries, produce only 1–2 wingless seeds each, and breakage is usually minimal during seed processing. Should it occur, the linear embryo occupying the majority of the seed length (Appendix I) will suffer the same fate as those of the other seeds discussed so far.
A monotypic genus, the embryo of a Cryptomeria japonica seed is linear and occupies the bulk of the seed length (Appendix I), so it is almost identical to seeds of the Pinaceae. If a sugi seed is broken, the same reservations as all the previous seeds must be applied.
Although seeds of Sequoiadendron giganteum (no drawing available) tend to be larger (3–6 mm) than those of Sequoia sempervirens (Appendix I) both contain linear embryos that occupy the bulk of the seed length. When mature, the brown wing (a tegumentary extension of the darker seed coat) of S. sempervirens is about equal in width to the seed. Even though redwood and giant sequoia seeds are not normally dewinged, should damage occur the same reservations must be applied to seeds of both genera, whether they are broken from either the chalazal or micropylar ends, and no matter what size the pieces of seeds represent.
An important timber species in the United States, but introduced into Europe in the mid-17th century both as an ornamental and for wildlife values, Taxodium distichum seeds are larger than all the seeds discussed so far (Appendix I). They are irregularly shaped with thick, horny, warty coats and projecting flanges. Just as in other gymnospermous seeds, baldcypress embryos are almost linear—slightly curved—and occupy the bulk of the seed length. If such seeds are broken either from the chalazal or micropylar ends the same reservations as with all the previous seeds must be applied.
The discussion so far has been on tree seeds that develop in, and are extracted from, cones. Special consideration is now given to two non-cone bearing gymnosperms, the yew and ginkgo (or maiden-hair tree) the latter being linked botanically to vascular cryptograms.
Although a major tree species, if only as an ornamental, yew trees do not produce cones, even though they are generally regarded as a member of the Coniferae (Dallimore and Jackson 1954). Taxus seeds form singly in scarlet, fleshy arils (outgrowths of the ovuliferous scales) that are similar in general appearance to berries, but they are not berries in the strict botanical sense. A line drawing of Taxus brevifolia, the Pacific West Coast yew is used for illustration purposes (Fig. 23). It is very similar to the European yew, Taxus baccata, except that its needles are shorter (hence the specific name brevifolia). Both species grow very well in graveyards when their roots reach decaying bodies.
The main difference in the internal morphology of a yew seed is that the embryo is proportionately much smaller that that of other species discussed so far. It is linear, but occupies no more than 50–60% of the seed length (Fig. 23). Thus even though the seeds are very hard (and difficult to germinate), and there is no wing to remove, should a seed be broken into a piece approximately 51–55% as measured from the chalazal end (Fig. 24) it will no longer have an intact radicle; as in other gymnospermous genera, yew also exhibits epigeal germination. Thus, such a piece of seed slightly larger than one-half the original size, while classified as a pure seed according to Rule 184.108.40.206.2 has zero chance of producing a new plant.
Conversely, if the yew seed is broken at 51–55% from the micropylar end (Fig. 25) there is a possibility that the embryo might remain relatively undamaged—only the tips of the cotyledons will have been lost—and germination might occur. As foresters working with yew seeds are well aware, germination of Taxus seeds can be very difficult to induce, requiring many months, up to a year or more, of moist pre-chilling. It is doubtful that broken seeds would survive such prolonged stimulation. If a yew seed is broken at around 75% of its original length (Fig. 26), and even more so at 90% (not illustrated), as measured from the chalazal end it will no longer have an intact radicle. Should the seed become broken at 75% (Fig. 27) or 90% (not illustrated) of its original length as measured from the micropylar end, the embryo may remain intact. If broken lengthwise the embryo may remain intact (Fig. 28), but the exposed megagametophyte and embryo may not withstand extended pre-chilling, and the seed will likely perish. Yew seeds, like those of other trees, must be collected when there is a sizeable crop, and then placed in dry, cold storage until they are prepared (pre-chilled) for sowing. Even if they do survive in storage, what chance does a broken yew seed have of producing a new plant? Especially if it does not contain the germ.
Differing from the Coniferales or Coniferae, especially in that its method of fertilization is effected by motile male sperms, Ginkgo is linked to the Vascular Cryptograms (ferns and their allies) (Dallimore and Jackson, 1954). Other workers regard it as a deciduous gymnosperm (Shepperd 2008). Single naked ovules ripen into large, drupe-like seeds with fleshy, smelly outer layers, and a thin, smooth, cream-coloured, horny inner layer. Embryo ripening continues in a large percentage of the “fruits” over winter, after they have fallen to the ground.
Internally, these fruits comprise a linear embryo (Appendix I) that occupies only 25–30% of the length of the seed, situated at the opposite end from the attachment scar, and surrounded by endosperm (2n). Like the yew, if a ginkgo seed is broken around 60% of its original length from the scar end, the entire embryo will be lost in the smaller piece (smaller than one-half the original length). The piece larger than one-half its original size has zero potential for producing a new plant because the embryo is not present, but Rule 220.127.116.11.2 says it must be regarded as a “pure seed.” If the seed is broken at around 60% from the opposite end, so that the piece contains a complete embryo, it is unlikely to produce a new plant not only because the exposed surface of the endosperm will cause the piece of seed to perish in storage, but also because the elongating embryo (if that occurs) will push the cotyledons out of contact with the endosperm and growth will cease. Normal germination is epigeal, but since there is no resistance from the chalazal end, the radicle will not emerge via the micropyle. Thus, this piece of seed, despite the intact embryo, has zero potential for producing a new plant. Even if larger pieces—75% or even 90%—of the original size containing the entire embryo are formed, the same limitations will apply.
It must be clear by now that there is nothing to commend broken gymnospermous seeds of any size, even up to 90% of the original size, as qualifying as “pure seeds,” even if they are sown soon after collection. For yew and ginkgo, unless the correct piece of seed is sown, that is, the one containing the embryo/germ, no germinant will be forthcoming. For all seeds discussed so far, the application of Rule 18.104.22.168.2 is nonsensical.
Even with the seed coat merely cracked, the internal tissues of all damaged seeds are subject to fungal and bacterial infections. The more tissue that is exposed the greater the likelihood of some form of infection. Intact seeds bear such spores in their seed coats, but the internal tissues may not be affected until the seeds begin to germinate. In germination tests of many coniferous species, especially Abies, the presence of Mucor and Penicillium can be substantial, and germinants may be abnormal as a result. With this knowledge, when a crack in the seed coat/testa is visible to the analyst, it must not be classified as a “pure seed.”
In most instances, the effect of Rule 22.214.171.124.2 for angiospermous tree seeds is not the same as it is for gymnosperm genera. For discussion purposes, seeds of angiospermous genera have been organized into two groups based on information contained in the “Woody Plant Seed Manual” (Bonner et al., 2008), as follows:
endospermic, which includes Cornus, Fraxinus, Gleditsia, Ilex, Liriodendron, Platanus, Tilia.
non-endospermic, which includes Acacia, Acer, Aesculus, Ailanthus, Alnus, Betula, Carpinus, Castanea, Corylus, Eucalyptus, Fagus, Populus (rudimentary endosperm only), Quercus, Robinia, Salix, Sophora, Tectona, and Ulmus.
Representative illustrations for each group, rather than all genera, will be discussed. Illustrations for other genera can be found in Appendix II.
The internal structures of seeds of Cornus, Fraxinus and Platanus closely resemble those of the gymnosperms in that there is a linear embryo that occupies the bulk of the seed length.
In Cornus seeds the embryonic cotyledons are thick and wide on an embryo that occupies 80% or more of the length of the “bony stone” surrounded by endosperm (Fig. 29). Occasionally a stone may contain two embryos as shown in the transverse section (B), or just a single embryo (C).
If such a seed containing a single embryo (Fig. 30) is broken so that a piece of seed 51–55% of the original length as measured from the chalazal (cotyledon) end of the seed, essentially all of the hypocotyl and the primary radicle tissue will be lost (Fig. 31). The endosperm will also be exposed, so the potential for a new seedling will be zero.
Conversely, should the break occur at 51–55% of the original size measured from the micropylar (radicle) end of the seed (Fig. 32), most of the embryo will be lost, and the endosperm will be exposed. Should the embryo remnant elongate it will emerge toward what remains of the chalazal (cotyledon) end of the seed because there will be no resistance to cause the radicle to exit via the micropyle; like gymnospermous seeds, germination is epigeal. Growth will be limited due to the lack of an energy source created by the missing cotyledons. Thus, even the short-term potential for a new plant will be zero. But Rule 126.96.36.199.2 tells the analyst this must be declared a “pure seed.” Once more, the inconsistent application of Rule 188.8.131.52 must be noted regarding separated cotyledons.
Even with pieces of seeds measuring 75% of the original size from either end (Figs. 33 and 34) there is no possibility for a new plant to be produced for exactly the same reasons. Although the embryo may not be damaged if the seed is broken at 90% from either end (Figs. 35 and 36) the endosperm will be exposed and viability likely lost. So the chances of producing a new plant are slim. Similar concerns must be expressed for a seed broken along its length (Fig. 37).
Again, the analyst will easily recognize these pieces for what they are. But, in all cases, Rule 184.108.40.206.2 requires the analyst to classify these pieces as “pure seeds.”
Ash fruits are elongated, winged, single-seeded samaras borne in clusters. Individual seeds vary in size, the one shown here of green ash (F. pennsylvanica) is approximately 15 mm long and the embryo occupies 90% or more of this length (Fig. 38). Germination is again epigeal, so if the seed is broken at 51–55% of its original length measured from either end, a major portion of the embryo will be lost: either the entire hypocotyl and primary radicle (Fig. 39), or the bulk of the cotyledons (Fig. 40) that are needed to provide energy for growth. In both cases, the internal tissues will be exposed. The effect of breakage at 75% from both the cotyledon and micropylar ends is shown in Figs. 41 and 42, respectively.
American sycamore seeds (Platanus occidentalis) (Fig. 43) closely resemble ash seeds in their internal structure—an elongated linear embryo from which significant portions will go missing if the seed is broken at 51–55% from either end (Figs. 44 and 45).
In both genera, even if the pieces of seed, from either end, measure 75% of the original size (Figs. 41 and 42 (Fraxinus), 46 and 47 (Platanus) there is no possibility for a new plant to be produced for exactly the same reasons. Internal tissues will be exposed so broken seeds will perish in storage. Again, these “pieces of seeds” are easily recognized for what they are but, in all cases, Rule 220.127.116.11.2 requires the analyst to classify them as “pure seeds.”
Linden embryos also occupy the bulk of the seeds, but they are far from linear (Fig. 48). It is clear that should a seed be broken from either end, at 51–55% (Figs. 49 ands 50), at 75% (Figs. 51 and 52) or even 90% (not illustrated), there is no possibility for a new plant to be produced for exactly the same reasons given above for Cornus, Fraxinus and Platanus. Exposure of the internal tissues will cause such broken seeds to perish during storage. Despite such “pieces of seeds” being easily recognizable, Rule 18.104.22.168.2 requires the analyst to classify them as “pure seeds.”
Although they depend on endosperm (2n) tissue to provide the energy for germination, seeds of the other three genera in this group differ in that their embryos are small: relative to overall external length of each seed, they occupy approximately 15% in Gleditsia (Fig. 53), less than 10% in Ilex (Fig. 54), and 20–25% in Liriodendron (Fig. 55). Thus, broken seeds present somewhat different problems.
After any amount of breakage from the chalazal end of the seed (the opposite end from where the radicle would normally emerge—epigeal germination), even if the piece is 75–90% of the original length, the embryo structure is likely to be lost within the piece “smaller than one-half of the original size” which must be classified as “inert matter.” In each case, despite the absence of the embryo, the “pieces larger than one-half the original size,” Rule 22.214.171.124.2 requires the analyst to classify them as “pure seed.”
If the seeds are broken from the micropylar end, so that the embryo is contained within the pieces, any “piece of seed larger than one-half the original,” i.e. a “pure seed,” has a chance—but not a very strong one—of germinating. Whether a normal germinant would result is unknown. And this would only apply if the seeds were sown or germinated before being placed in storage.
Both the impact of seed storage, already referred to frequently, and the designation of which piece of seed is greater than one-half the original, will be discussed more fully at the end of Part I.
In all cases, the identity of which piece of seed is being classified should be important. However, as will be discussed in Part II, not only has this detail not been taken into account, it has actually been denied to the analyst.
The embryo fills the entire seed coat in seeds of all these genera, the bulk of the tissue being the essential cotyledons (hypogeal germination); in comparison, the radicle and hypocotyl are diminutive, in many cases no more than 10–20% of the overall seed length, even smaller in Salix and Tectona. To illustrate the damage that will occur if these seeds are broken, focus is placed on Corylus and Quercus—hypogeal germination—and Alnus and Fagus—epigeal germination. To complete the picture, a special mention will be made of a tropical tree seed, Tectona (teak). Illustrations of the other genera in this group can be found in Appendix II.
The hard-shelled nuts of the hazel are quite large (Fig. 56), and are almost completely filled by the cotyledons (hypogeal germination). However, the hypocotyl and radicle occupy no more than 20% of the length of the seed at the micropylar end. As in the honeylocust, holly and tuliptree seeds discussed earlier, even a piece of a hazel nut that measure 75–80% of the original length of the seed measured from the chalazal end will not contain the hypocotyl and radicle (Fig. 59), let alone a piece only 51–55% of the original (Fig. 57). Despite the complete absence of embryonic structures, Rule 126.96.36.199.2 dictates that they must be classified as “pure seeds.”
In contrast, seeds broken in the same proportions measured from the micropylar end (Figs. 58 and 60) might produce a seedling, but it may not be a vigorous one since its cotyledonary-source of energy has been reduced and, because the internal tissues have been exposed, it may not survive storage. Once more, such pieces must be classified as “pure seed” according to Rule 188.8.131.52.2.
Alder seeds, represented here by the quite small-seeded species, Alnus rubra (red alder) (Fig. 61), are produced in cone-like strobiles and are easily extracted. Air dried, they can be stored for 2 years in sealed containers, but if dried to less than 10% moisture content (m.c.) they hold their viability for 10–20 years when stored at below freezing in sealed containers. They do not appear to be readily broken during extraction and processing, but Figs. 62 and 63 illustrate the damage that could happen to the internal structures if the seeds are broken.
Because the germ is so miniscule, even seeds broken at 75% of their original length measured from the chalazal end will not produce a new plant (Fig. 64). Yet such “pieces of seeds” must be regarded as “pure seeds” according to Rule 184.108.40.206.2. It is irrelevant to consider the effects of storage on such “pieces,” including seeds that have suffered longitudinal side breaks (not illustrated). Even at around 90% from the chalazal end (Fig. 65), germination is doubtful because the radicle/hypocotyl probably has been damaged. As in other species, seeds broken 51–55% (or more) of their original length as measured from the micropylar end might germinate if they are sown soon after collection and processing. However, it is doubtful they would survive below freezing storage at less than 10% m.c.
Acorns vary in size from 6 to 37 mm in length, those of Quercus rubra, the northern red oak (Fig. 66), being quite large; like the fruit of the black oaks, those of the red oaks require two years to mature. There are two fleshy cotyledons—no endosperm—that occupy the bulk of the acorn with the germ developing very close to the micropyle. So, if broken more than 50% of the length from the micropyle (Fig. 67), that is, a “piece of seed larger than one-half the original size,” there is a good chance of obtaining a new plant. In fact, the official germination test method involves soaking acorns in water for 48 hours, then cutting off roughly one third of the fruit from the cotyledon (cup scar) end, and planting the cut surface in wet sand. When the radicle appears and has grown down the side of the acorn to reach the surface of the sand, it is deemed to have germinated.
However, if the piece of acorn comprised 75–80% of the length of the nut from the cotyledonary end (Fig. 68), it would lack the germ and would have no potential for producing a new plant. But it must be classified as “pure seed” according to Rule 220.127.116.11.2. Even intact acorns are “recalcitrant” seeds (the term “less orthodox” preferred now) when it comes to storing them for any time. That is, they cannot tolerate desiccation below a high minimum moisture content—up to 45–50% in white oaks, somewhat lower in red and black oaks—making them very difficult to store. A side break (not illustrated) would exacerbate this condition. White oak acorns need to be collected soon after they have fallen from the tree to retard early germination. For these two primary reasons broken acorns have no chance of surviving any duration of storage and have no value for producing new plants. Pieces of acorns of any size are not “pure seeds.”
It should be clear by now that if seeds of Fagus grandifolia (American beech) (Fig. 69) are broken at approximately 75–80% from the cotyledon end (Fig. 70), there is no chance of obtaining a new plant because the very small germ that occupies only the narrowest part of the nut at the micropylar end, has been lost. Conversely, there may be a faint chance of a germinant if the nut is broken more than half way from the micropylar end (Fig. 71), an even larger piece increasing this possibility. Research on the European beech, Fagus sylvatica, has shown that its intact nuts can be stored for at least 6 years if dried properly and placed in sealed containers at temperatures from -5 to -15°C, which is long enough for reforestation operational needs. Similar studies on Fagus grandifolia are not known (Bonner 2008) or for broken seeds of either species, but broken seeds should be considered a write-off for producing new plants. Based on this, Rule 18.104.22.168.2 must not be applied. That is to say, pieces of beech seeds of any size must not be classified as “pure seeds.”
To illustrate that the questions surrounding pieces of tree seeds are not limited to temperate zone species, a tropical forest tree, Tectona grandis (teak), is included here. As Fig. 72 illustrates, the germ occupies less than 10% of the overall seed length. Thus, if the seed is broken so that a piece approximately 90% of the original size measured from the chalazal end is created (Fig. 73), the germ will be lost and there will be no possibility for obtaining a new plant. But which piece of seed is a decision denied the analyst (see Part II). Conversely, only a piece broken from the micropylar end (Fig. 74) has any chance of producing a new plant.
Because teak seeds are truly orthodox in storage behavior, viability of intact seeds may be maintained for up to 7 years at low temperature and relatively low moisture content (12%). Seeds stored in sacks in a dry warehouse maintained their viability for 2 years (Schubert and Francis, 2008). One method of extracting the 1–3 seeds from each fruit is by working a bag half-filled with dry fruits against the ground with a foot, then winnowing to separate the chaff. This would appear to be a very good opportunity for some seeds, small as they are, to be broken. There is no evidence that pieces of broken teak seeds maintain their viability as well as intact seeds, so why are they to be considered as pure seeds, especially if they are broken from the cotyledon end? Detailed information on many other tropical tree seeds can be found in Vozzo (2002).
The genus Eucalyptus requires special attention where Rule 22.214.171.124.2 is concerned. There are several reasons for this:
There are more than 523 known species of eucalyptus and 138 varieties, and new species and varieties are still being described (Krugman and Whitesell 2008). Among these species and varieties, as well as within a species, the length of fertile seeds varies from as small as 0.75 mm for E. camaldulensis, to 4.25 mm for E. citriodora. Fig. 75 illustrates the internal organs of an intact E. rudis seed, a small member of the genus.
For any given seed collection within a species (or variety) seed length may vary considerably. For example, in E. camaldulensis, one of the very smallest eucalyptus seeds, seed length may vary from 0.75 mm to 1.75 mm (Krugman and Whitesell 2008), i.e. by a factor of more than 230%.
PSD 60, as in all other definitions, requires that the pure seed fraction shall include pieces of seeds more than one-half the original size (with or without testa, of course). This means that the analyst is required to recognize broken seeds of E. camaldulensis possibly as small as 0.38–0.41 mm (380–410µ) in length, that is, approximately 51–55% of the original; at 65% of the original, pieces will be only 0.45–1 mm (450–1000µ) in length; and even at 75% of the original, pieces will be no larger than 0.56–1.3 mm (560–1300µ) long.
PSD 60 goes on to state that “in many” (of the more than 500) “species it is impossible to differentiate with certainty between seeds and ovulodes…” Does this not also mean that it is impossible to differentiate “with certainty” “pieces of seeds” possibly as small as 380–870µ (microns) long, even if they are distinguishable from the ovulodes? In other words, how can a piece of seed be recognized “with certainty?” What power microscope must the analyst use to attempt this recognition?
Even if pieces of seeds can be distinguished from the ovulodes by the analyst, a piece of seed broken more than 90% of the original length as measured from the chalazal end will be useless for propagating a new plant, because the minute hypocotyl and radicle will be missing (Fig. 76). Although “orthodox” in storage behaviour, a eucalyptus seed broken at 95% from the micropylar end (Fig. 77), even if it can be identified properly by the analyst, stands little chance of surviving prolonged storage.
So why does PSD 60 include Rule 126.96.36.199.2?
Because the scientific principles that apply to Eucalyptus have not been understood by ISTA.
It is clear that the biological knowledge of eucalyptus seeds has been completely ignored, that there is no legitimate scientific reason for inclusion of Rule 188.8.131.52.2. The only reason that Rule 184.108.40.206.2 is included in PSD 60 is to make it consistent with the other 62 PSDs. In any event, the procedure for the germination test (by weight rather than by number) makes the purity test for this genus appear to be redundant.
Other angiospermous seeds are illustrated in Appendix II.
Unlike the farmer’s seed crop plants, most of which produce annually, tree seed crops are periodic, and usually unpredictable. Whereas some individual trees may produce some cones or fruits every year, there may not be enough to warrant the expense of their collection on an annual basis. Most trees, most stands of trees, produce sizeable seed crops erratically, sometimes every second, third, or fourth year, or even less frequently, depending on the species and the geographic area in which the trees are growing. The terms “bumper crop” years, or “heavy mast” years, are commonly used to indicate, based on pre-collection inspections, that the crop is collectible, meaning it is worth the expense and effort of bringing it into the processing plant. In British Columbia it has been documented that only 8 “collectible” crops of Douglas-fir seeds occurred over 40 years (Lowry 1966). Meteorological conditions during the year of reproductive primordia formation, and in the following year when pollination, fertilization and seed maturation occur have major impacts on the amounts of seeds produced on forest trees (Eis 1973; Owens and Molder 1985). In contrast, teak trees (Tectona grandis) produce good seed crops more or less every year (Schubert and Francis 2008).
In the hemlocks, (Tsuga spp.), there are physical as well as biological constraints to producing cones of any quantity less than 2 years apart. This is because the female reproductive primordia are formed at the tips of branches and branchlets. Having produced a good crop on most if not all branch/branchlet tips this year, the mother tree must grow vegetatively for a year to produce fresh tips. Thus, at least a year must pass before this particular mother tree can form fresh reproductive primordia. Development of these are at the mercy of meteorological conditions over the following 2 years.
Compared to the farmer who may drive his combine harvester around his more-or-less level fields adjoining his farm house, the forester must make forays into the hills, perhaps to the summits of local mountains. Before doing so, the forester must make certain that gathering together the required collecting crew, equipment (including safety equipment) and supplies is worth the cost of travelling, often many kilometres, to the collection site. How to plan and organize cone collections, as well as guidelines for collecting, have been published (Dobbs et al. 1974; 1976; Edwards 1981a, 1985; Eremko et al. 1989; Portlock 1996).
Cone collecting of Douglas-fir and other regional conifer species by helicopter was pioneered in British Columbia (Camenzind 1990), and is now also used in other regions of the Pacific Coast (and probably elsewhere). This method (Fig. 78) permits seeds to be harvested from regions that are inaccessible overland by road. Clearly, the cone crop, and the seed crop contained therein, must be large enough to warrant the use of this method, not only because of the cost, but also because of the danger involved. Whatever the collection method, for any given seed source as many cone and seeds as possible have to be collected, because there may not be another crop for several years and annual reforestation targets have to be met.
Once the seeds have been extracted from the cones or fruits, they must be cleaned. This is the stage at which seed damage is most likely to occur. The cleaned seeds must be conditioned and placed in storage to meet future reforestation requirements. The sample submitted to the testing laboratory and which arrives on the analyst’s purity table, has been withdrawn from storage. This brings us to a crucial issue for pieces of forest tree seeds.
Literally thousands of research papers, entire libraries, have been written on seed storage, especially tree seed storage. The principles and practices of forest tree seed storage in general have been recently reviewed by Bonner (2008). This includes the most up-to-date information for all the gymnospermous and angiospermous genera included in the Rules. An earlier, excellent source is Wang (1974).
Thirty or so years ago forest tree seeds were classified either as “orthodox” or “recalcitrant” for storage considerations. Currently, “orthodox” and “recalcitrant” are viewed as extremes of a continuum, and terminology is moving away from “recalcitrant” to “non-orthodox.”
Coniferous seeds are regarded as “orthodox,” meaning that intact seeds can withstand being dried to low moisture contents in the range of 5–10% of their fresh weight and held for several years at -17°C without losing their viability. Below 5% m.c. autoxidation is likely. In contrast, many angiospermous seeds are “non-orthodox,” meaning that they do not take kindly either to being dried or to being refrigerated, and their viability suffers drastically and rapidly. Oak acorns (Quercus) are borderline “non-orthodox,” while chestnuts (Castanea) are very “non-orthodox.” Seeds of these genera, and Aesculus, are highly perishable even when intact.
Even for seeds of species regarded as being orthodox for storage, the role of the seed coat, or testa as ISTA prefers, is crucial. The longevity of coniferous seeds that survive being dried to low moisture contents and refrigerated depends upon their seed coats remaining intact. This is the key.
Structurally the seed coat is an inactive (non-living) covering that imbibes moisture rapidly when the seeds are prepared for germination, but which more importantly protects the internal tissues. In gymnospermous seeds these tissues are the female megagametophyte from which the embryo derives it source of energy for germination, and the embryo from which a new plant may be (but not always) derived. The seed coat acts to prevent germination until climatological conditions are advantageous. That is, in large part the seed coat is the cause of seed dormancy. It has been demonstrated in noble fir (Abies procera in North America, Abies nobilis in Europe) that chipping the seed coat at the micropylar end of the seeds, then allowing the seeds to imbibe water, brings on rapid germination without need for pre-chilling (Edwards 1969). However, if the seed coat is damaged in any way, even cracked, it loses its protective-envelope abilities and seed viability suffers if and when the seeds are returned to storage. Cracks or other breaches of the seed coat also allow microorganisms to enter. Respiration increases (Leadem 1993) until moisture levels have decreased to prevent further gas exchange. If this happens when the seeds are merely cracked, what chance is there for seeds that have been broken into pieces, no matter what proportion the piece is relative to the original size of the seed?
As already discussed, the seed coat acts to prevent fungal and bacterial infection. Damage it and the seed likely loses its viability to disease. Even with the seed coat merely cracked, the internal tissues of all damaged seeds are subject to fungal and bacterial infection. The more tissue that is exposed the greater the likelihood of some form of infection. Even intact seeds bear such spores on/in their seed coats, but the internal tissues may not be affected until the seeds begin to germinate, and the germinants may be abnormal as a result. With this scientific knowledge, as claimed in the Introduction to the Rules, why must the analyst classify damaged seeds as “pure seeds?”
“Non-orthodox” (recalcitrant) seeds, with their high moisture contents, are potentially very easily damaged during seed handling. According to Bonner (2008), the most important non-orthodox species in North America are the oaks (Quercus spp.) that have single-seeded fruits (acorns) with rather well-protected embryonic axes because of their strong outer covering structures. However, these coverings may become damaged, and the acorns broken into pieces if care in handling is absent. In sharp contrast, the seed of the silver maple (Acer saccharinum) has a large embryo protected by a soft pliable pericarp that is very susceptible to bruising during seed handling (Bonner 2008). Rough handling may break this seed into pieces.
The principle objective of storage is to reduce seed metabolism as much as possible without damaging their viability, and to prevent attack by microorganisms. The ideal metabolic rate during storage will conserve much of the stored energy reserves (needed for germination), yet allows the seeds to maintain the viability of the embryos. If seeds are broken into pieces, even if the outer coverings are merely cracked, let alone totally removed, internal changes include a loss in moisture content and an increase in respiratory processes that rapidly lowers the integrity, i.e., the viability, of the embryos.
Thus, when the ISTA Rules state that a “pieces of seed units larger than one-half their original size” must be regarded as a “pure seed” for 41 genera of Forest Tree Seeds (Table 1), the question must be asked: who wrote this Rule, and, on what scientific knowledge is it based?
Throughout this review, it has been emphasized that the Rules advertize that a “pure seed” means a “good seed,” i.e., one that, at least visually, has potential for producing a new plant (see Reminders). Churchgoers will be familiar with the 18th century German hymn “Wir Plügen” (words by the German poet Matthias Claudius, 1782, music by the German composer Johann Abraham Peter Schulz, died 1800) that in English begins:
We plough the fields and scatter the good seed on the land…
The emphasis here is on scattering (i.e. sowing, not planting) the “good seed” to produce a new crop of plants. Thus, more than 200 years ago farmers were anxious to sow “good,” i.e., potentially viable, seeds. What would be the point of sowing pieces of seeds that were not viable? Two hundred plus years ago, or even now?
When production of nursery seedlings for reforestation peaked at 265,000,000 plants, as it did in British Columbia (BC) in 2015, nursery managers would not be very happy to find they were saddled with pieces of seeds that are useless. However, the BC Ministry of Forests collects, processes and tests its seeds in-house, the latter following the ISTA Rules in principle, but not applying Rule 220.127.116.11.2 since seeds are provided to provincial nurseries. Seedlots that showed unusual amounts of impurities, including broken seeds, would be, and still are, recleaned. This is the practice at most if not all modern forest seed processing plants and nurseries. Particularly at nurseries that grow upwards of 14 million seedlings in mini-containers, such as is shown in Fig. 80. Fig. 81 shows the containers, or cavities as they are known, with spruce seedlings.
To be cost-effective, this type of seedling production requires a plant in each and every cavity. Even with highly pure seedlots germination may not be sufficient to guarantee a seedling from every seed sown, so to avoid empty cavities two or three seeds maybe sown in each cavity. Research has developed guidelines for the numbers of seeds to be sown based on laboratory germination performance. If more than one seedling appears in the cavities they are culled leaving the most vigorous plant to grow. Other research studying the effect such culling has on the genetic makeup of the final seedling crop, that is, the genetic base of the new forest, has also been conducted (El-Kassaby et al., 1993.)
The main issue is that broken pieces of forest tree seeds are not only useless in this system, they add to the costs (Edwards, 1981b).
The previous discussion illustrates a situation that has existed in the International Rules for most of the 20th century. Based upon this review (with more to follow) it is hoped that the ISTA purity test can be brought into the 21st century.
Seeking the origin of what is now Rule 18.104.22.168.2, a crucial 1965 report concerning the purity test (Proc. ISTA vol. 30) (see literature cited for full reference) by Prof. Dr. Harald Esbo (Statens Centrala Frökontrollenstalt, Solna, Sweden), who became President of ISTA 1965–1968, is quoted at some length as follows:
Concerning ‘Pure seed’, two different basic principles have been under discussion for many years. Up to 1950 the so called ‘Stronger method’, abbreviated S.M., was prevalent and prescribed by the ISTA rules, but in that year the so-called ‘Quicker method’ (Q.M.) was agreed upon by the ISTA Congress in Washington. According to S.M., only seeds which could possibly give rise to normal seedlings were considered pure seed; whereas Q.M. is including all questionable, damaged or badly developed seeds into the pure seed fraction leaving the evaluation of live or dead to the germination test. As the new method was saving time it was named Quicker Method. Nowadays this method is quite predominating. According to ISTA rules, pure seed includes all varieties of each kind under consideration as stated by the sender or found by the laboratory test, also,
undersized, shriveled or immature seeds
pieces of seeds more than half their original size
fruits whether they contain a true seed or not unless it is readily apparent that no true seed is present
and free caryopses.
There cannot be any doubt that Dr. Esbo (1965) was declaring that anything in the working sample that resembles a seed, even a clearly diseased or shriveled seed, except for a piece of seed that is less than one-half its original size is to be called a “pure seed.”
Where is the science claimed by ISTA to support this? Is this concept not scientifically bankrupt?
This concept is scientifically bankrupt.
Dr. Esbo then went on to state:
No doubt Q.M. has diminished the influence of personal judgement and led to more uniform results and is really time-saving.” (Esbo, 1965).
The matter of “time-saving” is repeated in item ii). This will be discussed below, together with the claim of diminished “personal judgement.”
Also note the inconsistent use of “seed” and “seeds” throughout.
In the same 1965 publication, Dr. O.L. Justice (Market Quality Research Division, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland, U.S.A.) wrote that:
The story of the ‘Stronger Method’ and the ‘Quicker Method’ of testing for purity may well become a legend in seed testing. Briefly, Europeans contended that seed structures of the kind under consideration which were incapable of germination should be removed from the pure seed fraction and included with inert matter. The Americans and Canadians, on the other hand, believed that such structures generally should be left with the pure seed and the germination test allowed to determine their planting value. As a consequence, both the Stronger and Quicker methods were included in the original rules adopted in 1931, and retained until 1953 (ISTA, 1931). Dr. W.J. Franck of the Netherlands made a strong plea for adoption of a single purity procedure at the Washington Congress in 1950. This and similar representations by the late Dr. H.A. Lafferty of Ireland in 1963 paved the way for general acceptance of a single method of determining purity.” (Justice, 1965.)
The above quotes are from two pivotal papers. The key here is the 1950 Congress being held in Washington (D.C.) at which many members of the AOSA would have been present. A large proportion of these individuals probably enjoyed membership in both AOSA and ISTA as many do at present. It is worth noting that the AOSA Rules were first promulgated in 1908, almost a quarter of a century before the ISTA Rules were first adopted in Wageningen in 1931, so the Q.M. is likely to have been well established within the AOSA Rules long before the 1950 Congress. So, as Drs. Esbo and Justice reported, the North American contingent held sway over the Q.M.
But why did the Americans and Canadians believe that seed structures which were “incapable of germination” should be left with the pure seed, leaving it to the germination test to determine their planting value? Also, exactly what did Dr. Justice mean by “the story… may well become a legend in seed testing?” Perhaps the current review is part of that legend.
Dr. Esbo stated that it was not until 1950 that the ‘Quicker Method’ only was agreed upon at the Washington Congress. Previous documents show that the “Piece of seed” issue had been in the ISTA Rules since at least 1938 after adoption by the General Assembly at Zürich in 1937. Dr. Justice noted that both the Stronger and Quicker methods were included in the original rules adopted in 1931, and retained until 1953.
This is documented in Proc. ISTA Volume 10 (undated), Fourth Part (International Rules for Seed Testing), section II Purity (beginning on page 412) which provides a “Definition of pure seed according to the a) Stronger Method (S.M.)” and “b) Quicker Method (Q.M.).”
These original definitions read as follows:
Stronger Method (S.M.)
All seeds of the kind under consideration (in so far as it is possible to ascertain from their appearance alone) both fully developed and uninjured, as well as such injured or not fully developed seeds as may possibly develop normal sprouts, should be considered ‘pure seed.’ However, certain cases are defined below where, in the interest of uniformity and accuracy, it is desirable to deviate from this general rule.
These “certain cases” included Clovers, Grass seeds, Beet seed, and any insect-eaten seed… if the damage is confined to the endosperm, but if the radicle is injured the seed must be considered as “inert matter.”
It is important to note that even in 1938 the Rules spoke of injured (or not fully developed) seeds as pure seeds if they might yield a normal germinant.
As an addendum, “For grass seeds, those with injured germs so as to preclude any possibility of germination shall be considered as inert matter.” (There is no mention of forest tree seeds—because they came to the Rules much later.)
However, this appears to be a clear indication that at this time (1938) the S.M. purity test did consider the question of viability. But compare the Quicker Method as quoted below.
Continuing with the 1938 definitions, we read:
Quicker Method (Q.M.)
All seeds of the kind under consideration (in so far as it is possible to ascertain from their appearance alone) should be considered as ‘pure seed,’ regardless of whether they are shriveled, sprouted, cracked or otherwise injured, provided that in the case of broken seeds any fragment larger than one-half shall be considered as ‘pure seed’, while pieces that are one-half or less should be considered as ‘inert matter.’ In making the purity analysis the question of viability of the seed must not be considered.
(Note this last instruction regarding viability, a clear break from the S.M.)
Another contradiction regarding the purity analysis and viability, we find:
Valid for both methods (S.M. and Q.M.)
If a sample contains a great many severely injured, poorly developed or discoloured seeds, this fact should be reported on the international analysis certificate, and in such cases it is advisable to make a supplementary germination test in soil.
This special definition c) then speaks to Legumes, Grasses, mangel, beet and sugar-beet clusters, and goes on to allow that:
If the sample received for analysis contains seeds (intentionally or unintentionally) which closely resemble those seeds with which they are mixed, the separation of the pure seed and the admixed ingredient in the normal working sample may be slow and laborious, and in such cases the following quicker method is permitted.
What followed is an even “quicker method” using as few as 200 seeds to sort out the pure and admixed seeds, determine their percentages, and report them (admixed seeds) on the certificate.
As already mentioned, there was no mention of forest trees seeds in the original Rules. The actual date (possibly 1956) of their introduction to the Rules in uncertain as this review is written, but it must have been before 1961 when a Forest Tree Seed Number was published (ISTA 1961). Dr. Esbo mentioned the coniferae in his 1965 report. Tree seeds were introduced to the AOSA Rules in 1965. Unfortunately, for current review purposes, no access to ISTA (or AOSA) publications prior to 1965 is available.
These rather lengthy quotations have been included here to place the “Piece of seed…” issue firmly it in its historical context. Clearly, broken seeds have been a headache since day 1 (1938) of the ISTA (and probably 1908 AOSA) Rules, and especially in 1950. They continue to cause some problems even today, perhaps for different reasons. This review of the “Piece of Seed” issue is not the first; others have trodden the same path previously (see Ashton 2000), and the issue “transcends forest tree seeds,” to quote recent correspondence with the ISTA Purity Committee. As Dr. Justice (1965) indicated, the 1950 Washington Congress was aimed at cleaning up the confusion created by using both methods.
Dr. Esbo (1965) pointed out that the so-called Q.M. became the preferred one after 1950 but, as Dr. Justice noted, against European desires. While the “European desires” are not discussed further by either Esbo or Justice, it is obvious that the Europeans did not wish to adopt the Q.M.—and this must be perfectly clear—because the so-called Quicker Method simply buries, or hides, or disguises broken seeds in the pure seed fraction, so that they are no longer accounted for on the certificate as they were when the S.M. was used. Yet if seeds had been “admixed” with other seeds, this was not only to be determined, but reported on the certificate as called for in definition c) above for both methods.
Dr. Justice commented that when the Q.M. is used, it is left to the germination test to determine the “planting value” of the seeds. Since it is still the method used today, it is necessary to ask if the Q.M. is really doing its job of determining the purity value of the seeds for planting/sowing, or is it abrogating its responsibility to the germination test? There appears to be some contradiction here that deserves more attention.
For what purpose are seeds of any plants tested? Does not the above represent a major contradiction of terms for testing? Why conduct a purity test if it offers no (or very little) assistance in determining the value of the seeds for growing new plants? Is such a test not a waste of time?
It may be inferred that by 1950 broken seeds had become an even more significant issue than previously (1930s) for producers of crop seeds, and ISTA was persuaded (by the North Americans) to do something about it. There is a suggestion here that pressure of a non-scientific nature was brought to bear.
Most importantly, we must ask: Is this practice honest? In other words: is it not deceitful to hide broken seeds in the pure seed fraction? How happy is the buyer of ISTA-certified forest tree seeds to find that, despite a high purity percentage, the poor germination is due to bits of seeds that are useless?
In any case, there was another option in 1950 that would have been completely supported scientifically, would have satisfied the need for speed, and which could have been applied to forest tree seeds when they were introduced to the Rules. It is tempting to call this the Really Quicker Method (R.Q.M.) although it does involve a little bit of paper work. A definition (similar to those for the S.M. and the Q.M.) might read as follows:
The advantages of the R.Q.M. include the gain in speed because the analyst does not have to judge (even though this judgement may take only a few seconds) if pieces of seeds are larger or smaller than one-half the original size, so another analyst working on a sample from the same seedlot is much more likely to agree with the result. Because of this, Dr. Esbo’s claim that the Q.M. has really “diminished the influence of personal judgement,” is highly dubious. Again, see Ashton (2000).
Consider the following hypothetical example using the same working sample in each case:
Case 1: Using S.M.
Broken seeds (all sizes)
(These are noted on the certificate)
Other crop seeds
(Pieces of seeds of all sizes already accounted for)
The subsequent Germination test showed 99%.
Case 2: Using Q.M.
(Broken seeds are not mentioned on the certificate)
The subsequent Germination test showed 90%.
So what are the differences between the S.M. and the Q.M. (and R.Q.M.)? Using the Q.M. (or R.Q.M.), we record:
12% increase in purity (over the S.M.).
1% increase in inert matter (due to pieces less than one half of the original).
9% decrease in germination.
The results of the Q.M. indicate that the lot appears to be very high in purity (99%) and not too poor in germination (90%). What seed purchasers do not know until the seeds are sown is that there is a substantial number of broken seeds—even though inert matter appears to be quite good at 2% because broken seeds are not recorded on the certificate—broken seeds do not germinate (perhaps they did not contain the germ), and which may clog up their modern seed sowing machinery. Alternatively, had the R.Q.M. option been used the same increase in purity, the same increase in inert matter, with identical germination results would have been obtained—at the expense of recording the fact that the sample contained broken seeds on the analysis certificate. So the seed purchasers would have been aware in advance that there were a number of broken seeds in this particular seedlot. But perhaps ISTA (and AOSA) did not (still does not) wish seed purchasers to know this.
As has already been explained, most modern forest nurseries use vacuum devices to sow (not plant) seeds in small containers (see Figs. 80 and 81). Having bits and pieces of broken seeds in the mix to be sown plays havoc with the production line, costs skyrocket because the line has to be shut down for cleaning. In a nursery producing millions of seedlings each growing season the problem can be immense.
How can undersized, shriveled or immature seeds, pieces of seeds more than one half their original size that do not contain the germ, fruits that may not contain a true seed, and diseased seeds be considered to be “pure seeds?”
See Esbo 1965
It would seem that perhaps some other pressure was brought to bear that was not scientific. That is, of a commercial nature. Whatever, it has probably never been documented.
The main emphasis placed by Dr. Esbo was on speed, hence the so-called “Quicker Method.” As has been seen, this is because in the Q.M. there are only 3 components (potentially 4 if weed seeds occur in the sample) to be sorted, whereas there were 5 in the S.M. Dr. Esbo claimed that:
No doubt Q.M. has diminished the influence of personal judgement and led to more uniform results and is really time-saving.
However, the proposed R.Q.M. would have been both quicker (than the S.M.) and would have completely resolved the “influence of personal judgement” (in the Q.M.). (See Ashton 2000).
Dr. Esbo noted (in passing as it were) that whereas the S.M. only permitted seeds that could possibly give rise to normal seedlings were to be classified as pure seeds, the Q.M. totally disregards this—in the interests of speed—leaving the evaluation of live seeds to the germination test. As already questioned, does this not mean that the purity test is abrogating its responsibility to the germination test, and is not determining the planting/sowing value of the seeds?
So why was speed so important?
A very slow weighing procedure.
In the early days of seed testing, some 80+ years ago, purity analysts were limited to weighing the submitted samples, the working samples and the components thereof, using an analytical beam balance (Fig. 82). For today’s analysts who may not be familiar with this equipment, a brief description is in order.
It was a very sensitive instrument yielding precise weights, but it had to be used in a draught-free environment. As shown here, it came with its own glass-sided case; the front panel would be slid upwards (Fig. 83) to provide access to the weighing pans, then lowered to make the weighing and to avoid ambient air movements. Before using the balance the operator had to make certain that it was precisely leveled on the work bench using the adjustable screw feet in each corner underneath the case.
When not in use, the beam was lowered by rotating a knob (visible in the center of the lower edge of the case) anti-clockwise until the beam made contact with two supports (near its ends) to take the load off, and therefore protect, the knife edge. For weighing, the knob was rotated clockwise to lift the beam off its supports. With the beam balancing nicely on the knife edge, the analyst then had to make certain that the pointer (just visible in front of the white scale between to the two pans) was reading zero. To access the balance within its case, the front panel had to be lifted (Fig. 83) so that the small screws (counterbalances) visible at the ends of the beam could be turned clockwise or anti-clockwise as required until the pointer registered zero. Done with the beam lowered.
All these preparations had to be made before weighing could begin. The sample would be placed in the left pan (usually), then the beam raised by rotating the front knob, and weights added to the right pan. Weights were kept in a small box designed specifically for their use (Fig. 84).
These weights, usually made of brass, had to be used with considerable care, and were not to be handled except by the use of forceps, especially the smaller weights that consisted of cut pieces of metal (brass or other non-corrosive material). Such a precaution was necessary because handling them by hand, without forceps, could easily affect their weight, especially the very small ones. All weights, even the larger ones seen in the rear row of the box, had to be handled very carefully.
Before a seed sample was weighed it would be placed in a small container, usually a metal dish that would fit onto the balance pan. The “tare weight” of this container had to be determined in advance, its weight recorded so that it could be subtracted from the seed sample weight. In most instances, the tare weight had already been inscribed on the pan by the manufacturer, making life a little easier. Using such a dish also made removing the samples from the balance pan relatively easy. Again, the dishes had to be handled with care, usually using the same forceps.
Raising the front panel of the case, the sample to be weighed (in its dish) would be placed on the left-hand pan of the balance. With experience, the analyst would be able to guesstimate which of the larger weights to add (to the right-hand pan) to begin the weighing procedure. This was done with the beam lowered. The front panel of the case would then be lowered, gently, and the beam raised off its anchors. If the pointer did not register centrally on the scale, the beam would then be lowered, the front panel raised again, and the amount of weight adjusted. This process was repeated until the weight(s) in the right-hand pan exactly balanced the sample as shown by the pointer registering zero on the scale. The operator then had to lower the beam onto its anchors, open the case again, and remove the weights from the pan and record their total. Although not shown in Fig. 84, weights to fractions of a milligram could be achieved by this process.
Having weighed the submitted sample, and recorded its weight, the analyst would divide it to obtain the working sample on which the purity analysis was to be made. The working sample for that species (Rule 3.5) was weighed using the same process, and its weight recorded. The purity test proper would begin by separating the components of the working sample—pure seeds, crop seeds, other seeds, damaged seeds (using S.M.) and inert matter—and then weighing and recording each in turn. All this had to be performed in a draught-free room because the beam balance was especially sensitive to air currents. Hence the sliding, closeable front panel. When completed, the beam would be lowered one last time, and the weights (if they had not been dropped on the floor!) returned to their allotted spaces in the box, the box closed and put away for future use.
It will be readily apparent that this was a slow, laborious process; the purity analysis of a single submitted sample might take 30 minutes or more, even for an experienced analyst, to complete. Anything that could be done to speed up the process was most welcome. This is where the Q.M. really came into its own. By weighing only three components instead of five, the time spent per working sample was reduced by 40%. This is what Dr. Esbo meant when he claimed that the Quicker Method was “really time-saving.”
However, since the early 1960s electronic balances have come to the fore (Fig. 85). Although these need to be protected from air currents also—they also have their own cases—the time required for weighing the components of a purity analysis has been reduced to a fraction of that using the beam balance. Instead of minutes per component, each can be weighed in seconds. More modern electronic balances now print out the sample weight at the push of a button. Some may even be connected directly to a computer. In either case, the analyst does not need to record the weights, a time-saving factor in its own right. With electronic balances being readily available, there is no scientific or operational reason for not weighing broken seeds of any size, and reporting them. Therefore, Rule 22.214.171.124.2 has become completely redundant for forest tree seeds, perhaps for all types of seeds.
Having gained the superior weighing speed provided by electronic balances, why does ISTA continue to insist on using the Q.M. and not the S.M.?
See Esbo 1965.
As has been discussed in PART I, there is no scientific basis for calling broken forest tree seeds of any size “pure seeds.” That Rule 126.96.36.199.2 still has to be applied is merely a throw back to the status of the purity test when forest tree seeds were introduced to the Rules, when extremely slow sample weighing was carried out using beam balances. Modern balances have cut the work time required for a purity analysis to a fraction of what it used to be, and there is no excuse for not recognizing this and changing the Rules accordingly, at least for forest tree seeds.
On page 34 of his 1965 paper Dr. Esbo wrote:
As far as crop plants are concerned, all seed-like structures which according to the definitions already given can’t be classified as pure seeds, are included in inert matter.
Then follows a list of “such structures” including “seeds of coniferae with the seed coat entirely removed.” So forest tree seeds, at least coniferous seeds, had come up over the horizon, indicating that they had been included in the Rules prior to writing his report.
Further on, Dr. Esbo states that:
Common to all these categories of seed-like structures which are classified as inert matter is the fact that they are deemed as not to be able to give rise to a seedling.
Note that they are merely “deemed” to be useless for producing new plants, not that scientific knowledge says that they are useless.
Here is the purity test being used to assess growth potential, something that the Rules insist must not be taken into account—the purity test is not a growth test.
Again, in a subsequent paragraph when writing about weed seeds, Dr. Esbo states that seed-like structures which:
…by visual examination based on long experience can be evaluated with certainty as having no chance of giving rise to a plant should be deemed as inert matter.
Why is he writing this? The purity test is not a growth test. But Dr. Esbo seems to ignore this. But seed like structures… evaluated with certainty as having no chance of giving rise to a plant… certainly includes forest tree seeds of all sizes and all kinds.
Therefore, it must be said that Dr. Esbo lacked the scientific knowledge, and experience, that the current Rules insist upon (Rules, Introduction, page 1), scientific knowledge and experience that has firmly established that pieces of forest tree seeds of any size should be classified as inert (if not dead) matter, or simply as Impurities. This is not a growth test: it is scientific knowledge being applied.
Again, here in the Q.M. Dr. Esbo states that the analyst must make an evaluation of no chance of giving rise to a plant, that is, a viability judgement. While such “evaluation” or judgement is not a test per se, it does contradict the notion that the purity test is not a viability test.
The fact that the purity analyst is expected to distinguish between seed-like structures that are not able to give rise to a seedling, and those that may give rise to a seedling, Dr. Esbo’s claim that the “Q.M has diminished the influence of personal judgement” appears to be highly suspicious, contradictory, false and based entirely on innuendo.
As was illustrated in detail for Larix, in Part I, one analyst may classify a piece of seed measuring 51–55% of the original size, that is, more than one-half the original size based on a guess at the original size (see Fig. 8), (with a portion of the testa still attached, of course) as pure seed, while the next analyst, possibly in the same laboratory, may regard it as inert matter. Ashton (2000) reported that at a Workshop in Hungary in 1997, most participants estimated several fragments of Avena fatua caryopses as being greater than one half, but these fragments had been deliberately made to be exactly one half of the original seeds, and therefore should have been classified as inert matter. If this happens when analyzing the purity of wild oat seeds, not just at a Workshop, but also in the laboratory (again Ashton 2000), how inconsistent can matters become when analyzing the purity of forest tree seeds that may vary in size by more than 250% (see Fig. 8)?
Yet Dr. Esbo claimed that the Q.M. removes such inconsistencies.
These are just some of many contradictions.
But there are more. As quoted earlier, the so-called Q.M. includes “all questionable, damaged or badly developed seeds” (more than one-half their original size) in the pure seed fraction.
Expressed in other terms, the analyst must include any damaged seeds with the pure seeds so that they become hidden. Because nothing is written on the certificate (Rule 3.7) regarding broken seeds the seed buyer is hood-winked into thinking he/she is purchasing a crop with a high degree of purity. As shown in the numerical example earlier, the germination test will show this is not a top quality seedlot.
But is this not a highly questionable practice, and basically dishonest?
Besides, if ISTA was really interested in speeding up the purity test (as Dr. Esbo claimed) why not put all questionable, damaged or badly developed seeds of any size into the inert matter (or, preferably, Dead matter = Impurities). This would lower the resulting purity of the seeds, say from 98% to 90%, but the germination test result would be higher. Not only would this really remove any judgement on the part of the analyst (a serious concern of Dr. Esbo), but it would make the certificate more honest.
Elsewhere in his 1965 report, Dr. Esbo wrote that:
A reliable evaluation of the purity of seed as well as other properties can however be done only by people having a special education and a certain knowledge in botany and agriculture and by persons who are quite impartial and totally independent of consequences of the evaluation.
Here the operative words are people having a special education and a certain knowledge in botany and agriculture. Since tree seeds had begun to be introduced to the Rules when he wrote this, should not and forestry (and horticulture) have been added? Dr. Esbo had to be aware of some of these additions to the Rules because he makes reference to the coniferae. But it seems clear that, in 1965, this special education and knowledge in forestry was completely lacking in agricultural officiandos who were then controlling the Rules, and it appears to have been lacking over the past 70+ years (50 years since Dr. Esbo wrote his piece).
As mentioned earlier, by 1950 (the Washington Congress) broken seeds clearly had become a significant issue, especially for American and Canadian seed producers and ISTA was persuaded to do something about it. That is, some 63 years ago ISTA opted for speed over accuracy, precision and honesty in the purity test.
Was there a hidden agenda? Was there a commercial agenda? There certainly was no scientific agenda where forest tree seeds were concerned.
Exactly how was the “Stronger Method” of the purity test applied before the change in 1950? According to the version published in ISTA Proceedings Vol. 10, number 1, (undated), originally there were five groupings, i.e., “pure seed,” “crop seeds,” “weed seeds,” and “inert matter,” with broken seeds being set aside, weighed separately and reported on the certificate. In the “Quicker Method” there were only three groupings, i.e., “pure seeds,” “other seeds,” and “inert matter.” The original grouping “weed seeds” was deleted, “crop seeds” became “other seeds,” “pieces of seed larger than one-half their original size” were included (hidden) within “pure seeds,” while pieces smaller than one-half were included within the “inert matter.” Neither larger nor smaller pieces of seeds were accounted for on the certificate. By not doing so this saved a few minutes.
Basically, in the Q.M. anything and everything that was not classified as “other seeds” or “inert matter” was (and still is) to be considered as “pure seeds. Exceptions were to be made for certain cases of special types of damage to “clovers, grass seeds, beet seed clusters,” and even “insect-eaten seed”… provided said “damage is confined to the endosperm.” Seeds with damaged endosperm were to be included as “inert matter.”
In the very early years when both methods were employed, the main difference between the S.M. and the Q.M. appears to be that the S.M. paid no regard to the size of any broken seeds and all pieces were placed in a separate pile, and – most importantly – the weight of broken seeds was recorded on the certificate. In contrast, the Q.M. all along has required that broken seeds more than one-half their original size should be considered as “pure seeds” (Rule 188.8.131.52.2). This is a major difference, one that needs to be questioned now that the “requirement for speed” riddle has been exposed—and solved.
Additional attention needs to be drawn to the 1965 words of Dr. Esbo (President of ISTA 1965–1968) especially regarding item (c) above:
In order to achieve a high degree of uniformity in seed testing, which is one of the major aims of ISTA, it is essential that clear definitions of the different words and terms be settled and made available to all parties involved.
One of the aims of this review has been to make different words and terms clear. In English “seed” may be used as a collective singular, thus meaning many seeds. In doing so, the verb particles around it often become confused. For example, “this seed is to be sown next week” (only one seed?) or “these seeds are to be sown next week.” The use of “seeds” when referring to more than one seed is highly preferable, because the writer’s syntax becomes more consistently correct. Other languages may have similar, or lesser, difficulties. This may appear to be a very picky point, but if the Rules are to be precise, as Dr Esbo believed, the wording needs to be studied carefully.
All of this reflects the seed processing technology that existed 60+ years ago. It is assumed, perhaps incorrectly, that even for crop seeds major advances have been made and broken seeds are much less of a problem, or have been completely eliminated. If the latter is true then Rule 184.108.40.206.2 must be amended, if not extinguished.
From the reviewer’s personal experience, improvements in processing of coniferous tree seeds have advanced greatly during a 28-year career as a seed biologist. There were reports from a few seed producers that damaged tree seeds could still be found occasionally, but their frequency has greatly diminished. During the reviewer’s decade-plus tenure as manager of the ISTA-accredited laboratory CAN07, no broken seeds were found from local seed producers who sold their products internationally. Thus, the “Piece of seed larger than one-half the original size, with or without integument, provided a portion of the testa is attached” (Rule 220.127.116.11.2) issue basically became a non-issue, despite what the Purity Committee expressed in 2006 in an e-mail relating to proposed PSD revisions for a number of gymnosperm species (see below).
In reality, the issues regarding forest tree seeds and the Purity Test go beyond “pieces of seeds.” In PSDs 10, 12, 52, 53, 54, 55, 56, 57, 58 and 60, even intact seeds that are devoid of (“without,” or “entirely removed”) testa are regarded as pure seeds. In PSDs 11, 47, 49, and 50 intact seeds with only a portion of the testa attached are regarded as pure seeds. As was noted earlier, no definition of “a portion” is provided. Perhaps a “portion larger than one-half of the original?”
In PSD 51 “portion of the testa” becomes “part of the testa,” another example of inconsistency in wording.
What published scientific evidence is there that allows naked, or near naked tree seeds, to be regarded as “pure,” that is, good/sound seeds capable of producing new plants, especially if such seeds have been in dry, cold storage for any length of time, or have been infected with fungal or bacterial organisms? If there is such scientific evidence, it should be brought to everyone’s attention, especially that of this reviewer. However, this is grist for another mill.
What is the purpose of this long-winded review?
That the Rules continue to perpetuate the unscientific myth (or legend according to Dr. Justice, 1965) of Rule 18.104.22.168.2, was brought to the reviewer’s attention in 2006 when the Chair of the Purity Committee insisted on its inclusion in a proposal submitted to revise PSD 51 (Abies, Cedrus, Larix, Pseudotsuga and Tsuga). Whereas this demonstrated the Purity Chair’s attention to detail and correctness in drafting PSDs (new or otherwise), it served as a wake-up call regarding the ambiguity and scientifically bankrupt nature of Rule 22.214.171.124.2 as it is applied to forest tree seeds.
Is it not time for ISTA to move the purity test into the 21st century?
All forest tree seed analysts have the botanical and forestry education, as well as expertise and experience, so collectively they should be able to make a strong case for revision of the ISTA Rules as they are applied to forest tree seeds. Failure to do so in effect means that ISTA will be satisfied with the early 20th century status quo, that is, the Dark Ages for purity testing.
Based on the foregoing it is strongly suggested that the following statement be included in the Introduction to the Rules:
“Seed quality is a concept made up of different attributes. Seed is a living biological product and the methods used for testing must be based on scientific knowledge of the seed in question, as well as on the accumulated experience of seed analysts. The information gained from these tests must be aimed at providing information to the producer, the processor, the warehouseman, the merchant, the farmer, the horticulturalist, the forester, the certification authority and to the government or agency responsible for seed control, to determine if the seeds are of high enough quality to produce an abundant crop of the species under examination.
The main premise on which this review has been based is that the term “pure seed” means a good seed, that is, one that has potential for producing a new plant. Using copious line drawings to show the internal structures of forest tree seeds and how they are affected if the seeds are broken, it has been demonstrated that classifying pieces of tree seeds more than one-half their original size, even if they have the full quota of testa/seed coat (for that size of seed piece) as “pure seeds” is scientific nonsense. That this hiding or burying such broken seeds in the pure seed fraction in the name of speeding up the purity test is not only unethical, but is now completely unnecessary with the advent of modern seed weighing technology, and improvements in seed processing technology. Equipment, in the form of old-fashioned beam balances, appears to have been the main reason why the “Quicker Method” was singularly adopted more than 63 years ago. If ISTA is not prepared to return to the original “Stronger Method” it should at the very least consider adopting the proposed “Really Quicker Method.”
The discussion presented herein is the result of the reviewer thinking “outside the box.” That is, thinking that a pure seed of a forest tree species means a seed with the potential for producing a new plant. Because the purity test is not a growth test (despite what Dr. Esbo wrote in 1965), only the external visual features of the seed can be used in this assessment. These same external visual features will readily indicate to even an inexperienced analyst that the seed cannot produce a new plant if it has been broken into pieces of any size. It is painfully evident that Dr. Esbo’s “serious injury” should have been applied to broken forest tree seeds when they were introduced into the Rules. ISTA should explain why seeds (of any kind) that have been broken into pieces are not considered “severely injured” seeds.
The Rules require a thorough purging of the terminology used to describe seeds in the Purity Test, and to ensure that it is consistent and standardized throughout to ensure standardized testing.
In this, Dr. Esbo would be highly pleased.
It is proposed that ISTA reverts to the original so-called “Stronger Method” of performing the Purity Test on forest tree seeds.
The background for this proposal has been fully discussed in the main body of this review. The reasons are several and are summarized here:
Broken forest tree seeds of any size have no value for producing new plants.
Rule 126.96.36.199.2 was in place in the Rules before forest tree seeds were introduced, and was applied to them and has been applied ever since, with no consideration being given to tree seed structures, their biology, and what happens to these structures when seeds are broken.
ISTA has no excuse, no scientific or operational rationale for continuing to classify pieces of forest tree seeds more than one-half their original size even with a full compliment of the testa/seed coat still attached, let alone completely naked seeds, as pure seeds because the operational reasons for doing this have long since disappeared, especially since the introduction of new weighing technology.
ISTA must honour its claim in the Introduction to the International Rules for Seed Testing that test methods must be based on scientific knowledge, as well as the accumulated experience of those working in seed testing and quality control.
This will completely eradicate personal judgement on the part of different analysts, something that would have pleased Dr. Esbo.
It should be noted that Dr. Esbo can be blamed for many of the dubious esoteric Rules regarding pure forest tree seeds that ISTA continues to use. Clearly, Dr. Esbo lacked the scientific knowledge and experience with such seeds that the Rules insist upon. Also, he is responsible for many of the inconsistencies and contradictions noted above, matters he claimed he wished to see cleared up.
Failing this, that is, if the above in not achievable for policy or other dubious reasons:
It is proposed that ISTA adopts, as an alternative, the “Really Quick Method” of performing the Purity Test on forest tree seeds (and perhaps other seeds).
The background for this proposal has been outlined in the text. The main reasons are that:
The analyst does not have to make any judgement on the size (or lack thereof) of pieces of seeds, so the result of any test will be reproducible among different analysts.
This will actually speed up the test, although the “need for speed” is no longer a priority since weighing technology is vastly improved.
The presence of broken seeds, to be committed to the Impurities fraction, is to be recorded on the analysis certificate.
The relative amount of broken seeds could be recorded as “few” if a rapid visual judgement indicates that there are less than 10 pieces in the working sample, “some” if there more than 10 but less than 50, and several if more than 50. The analyst is not required to weigh the broken seeds.
As soon as possible, it is proposed that Rule 188.8.131.52.2 no longer be applied to forest tree seeds.
To achieve this,
It is proposed that the statement “Piece of seed larger than one-half the original size, without wing or integument, provided a portion of the testa is attached” be deleted from PSD 47.
It is proposed that the statement “Piece of seed larger than one-half the original size, provided a portion of the testa is attached” be deleted from PSDs 49 and 50.
It is proposed that the statement “Piece of seed larger than one-half the original size, without wing, with (but occasionally without) integument, provided a portion of the testa is attached” be deleted from PSD 51.
It is proposed that the statement “Piece of seed larger than one-half the original size, with the pericarp/testa partially or entirely removed” be deleted from PSDs 52, 53, and 58.
It is proposed that the statement “Piece of seed larger than one-half the original size, with or without testa” be deleted from PSDs 54 and 60.
It is proposed that the statement “Piece of seed larger than one-half the original size, with or without testa” be amended in PSDs 10 and 12 to read:
“Piece of seed larger than one-half the original size, with or without testa does not apply to forest tree seeds.” (PSDs 10 and 12).
It is proposed that the statement “Piece of seed larger than one-half the original size, provided a portion of the testa is attached” be amended in PSD 11 to read:
“Piece of seed larger than one-half the original size, provided a portion of the testa is attached does not apply to forest tree seeds.” (PSD 11).
It is proposed that the statement “Piece of seed larger than one-half the original size, with pericarp/testa partially or entirely removed” be amended in PSDs 55, 56 and 57 to read:
“Piece of seed larger than one-half the original size, with pericarp/testa partially or entirely removed does not apply to forest tree seeds.” (PSDs 55, 56, 57).
It is proposed that if pieces of forest tree seeds, of any size, are found in the working sample, they must be consigned to the Impurities fraction and a note of their presence must be made on the Analysis Certificate (amendment to Rule 3.7). See Proposals B and E.
It is proposed that ISTA standardize the text throughout the Rules.
Where more than one seed is the subject, the word “seeds” is to be used.
When speaking of an incomplete testa or seed coat, the word portion is to be used.
The Rules must explain why a broken seed (of any kind) is not a “severely injured” seed.
It is proposed that the Rules cease using the term “inert matter” in preference to Impurities.
It is proposed that future publications of the Rules cease italicizing plant names above the genus level.
Regarding other textural inconsistencies, there is no excuse for these to occur in a publication of this international stature. While the English word “seed” is a collective singular, its use often leads to errors in syntax. As explained in the main text, the statement that begins with “The seed is…” refers to one seed only since the singular form of the verb is used. If more than one seed is referred to, the statement should read “The seed are…” However, consistent use of “seeds” when speaking of more than one seed avoids this error.
Similarly, the word “portion,” which is used frequently in the current Rules, should replace any reference to “part.” In PSD 51, both part and portion are used.
The italicization of plant group names above the genus level flies in the face of taxonomical nomenclature principles. Throughout the text of the Rules italicization must be restricted to genus and species names only. For Rule headings, e.g. 3.2.1 Pure seed (following on the main heading 3.2 Definitions) a different type face, but not italicized, could be used. This review appears in a serif font. Thus, setting 3.2.1 Pure seed in a sans-serif font still sets the heading apart without italicization.
ISTA should also consider stepping outside the pure seed definition box to provide definitions of the words “pure” and “inert” as they are applied to seeds in general, but especially to forest tree seeds. As discussed under General Comments and Questions in the Introduction, “inert” does not necessarily mean Dead, at least not in the human frame. But since the impurities usually found in, say, a working sample of pine seeds may consist of needles (leaves), bud scales, cone scale fragments, soil particles, and other matter that are Dead, a definition of what ISTA understands by “inert” is in order. A change to “Impurities” would not only make matters much simpler, but would avoid the need for this (“inert”) definition And, are not “pure” seeds good seeds for producing new plants? If so, say so.
Dr. Esbo’s 1965 plea must be remembered, viz.,
In order to achieve a high degree of uniformity in seed testing, which is one of the aims of ISTA, it is essential that clear definitions of the different words and terms be settled and made available to all parties concerned.
“All Parties concerned” includes the seed producer/processor, the seed analyst and the seed user.
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Krugman S.L. and C.D. Whitesell, 2008. Eucalyptus L’Her. Eucalyptus. IN: Bonner et al. 2008: 504–512.
Leadem, C.L.1993. Respiration of Tree Seeds. In: Edwards, D.G.W., comp. & ed. Proc. Internat. Sympos. "Dormancy and Barriers to Germination". IUFRO Proj. Group P2.04.00 (Seed Problems): 1991, Victoria, B.C. Victoria: Forestry Canada, Pacific Forestry Centre: 57–66.
Lowry, W.P. 1966. Apparent meteorological requirements for abundant cone crop in Douglas-fir. For. Sci. 12: 185–192.
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Portlock F.T. 1996. A field guide to collecting cones of British Columbia conifers. British Columbia Tree Seed Dealers’ Assoc. Joint For. Can. B.C. Min. For.: FRDA II. 91p.
Porsild, A.E. 1967. Lupinus articus Wats. Grown from seeds of Pleistocene Age. Science 158: 113.
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Young, J.A. and C.G. Young, 1992. Seeds of woody plants in North America. Revised and enlarged edition. Discorides Press (an imprint of Timber Press, Inc.), Portland, OR. 407p.
University of Aberdeen, Scotland—B.Sc.(Forestry), 1959.
University of Washington, Seattle, WA—Master of Forestry, 1963. Thesis: The effect of soil type on growth of noble fir (Abies procera) seedlings.
University of Washington, Seattle, WA—Ph.D. (Forestry), 1969. Thesis: Delayed germination in noble fir (Abies procera) seeds.
Forestry Commission, Forest Research Station, Farnham (England), Seed Laboratory, Technician—1961–62.
University of Washington, College of Forest Resources, Seattle (Washington), Research Assistant—1959–1960.
University of Washington, College of Forest Resources, Seattle (Washington), Research Assistant and Teaching Assistant— 1963–68.
Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, Research Scientist—1968–1996.
Proprietor, FTB Forest Tree Beginnings, Consulting Company, Victoria, British Columbia—1996–present.
International Seed Testing Association (ISTA)—Official member (CAN07) accredited to issue International certificates of seed quality, 1975–1999, Pacific Forestry Centre, Canadian Forest Service, Victoria, British Columbia, Canada.
Member of the Forest Tree and Shrub Seed Committee, 1972–2006.
International Union of Forest Research Organizations (IUFRO), Research Group 2.09.00 (Seed Physiology and Technology)—member 1972–2002, Chairman 1991–2001.
Association of the Official Seed Analysts of North America (AOSA)—member of the Forest Tree Seed Committee.
Organization for Economic Cooperation and Development (OECD)—Official Representative for the Canadian Designated Authority for the scheme for certification of forest reproductive materials moving in international trade, 1983–1989.
Pacific Northwest Seed Certifiers Association—member, 1971–1990.
IUFRO Working Party S2.03-14 (Seed Legislation)—member.
Western Forest and Range Seed Council—member, past Chairman.
Canadian Tree Improvement Association, Tree Seed Working Group—founding member.
Canada/British Columbia Cone and Seed Committee—member, past Chairman.
British Columbia Tree Seed Dealers’ Association—associate member.
Member, Society of the Sigma Xi, University of Washington Chapter, 1964.
Distinguished Leadership Award, Extraordinary Service to Forest Tree Seed Science, American Biographical Institute, 1992.
Distinguished Service Award, International Union of Forestry Research Organizations (IUFRO), 2000.
New Forests, Tree Physiology
Annals of Botany
Canadian Journal of Botany
Canadian Journal of Forest Research
Forest Ecology and Management
Journal of Southern Forestry
Journal of Plant Physiology
Journal of Tropical Forest Science
Seed Science and Technology
Adjunct Professor, Department of Forest Sciences, University of British Columbia.
Chaisurisri K., D.G.W Edwards and Y.A. El-Kassaby. 1993. Accelerated aging of Sitka spruce seeds. Silvae Genet. 42: 303–308.
Chaisurisri K., Y.A. El-Kassaby and D.G.W Edwards. 1993. Genetic control of seed size and germination in Sitka spruce seeds. Silvae Genet. 41: 338–354.
Davidson, R.H., D.G.W. Edwards and O. Sziklai. 1985. Treatment and temperature effects on the germination of Pacific silver fir. Program and Abstracts, Northwest Scientific Assoc. Mtg. Montana Acad. Sci. Cont., Montana 1984, Authors Index no. 94.
Davidson, R.H., D.G.W. Edwards, O. Sziklai and Y.A. El.-Kassaby. 1995. Genetic variation in germination parameters among Pacific silver fir populations. Silvae Genet. 45: 165–171.
Dobbs, R.C., D.G.W. Edwards, J. Konishi and D.P. Wallinger. 1974. Cone picker’s manual. B.C. For. Serv./Can. For. Serv., Joint Rep. No. 1, 13p.
Dobbs, R.C., D.G.W. Edwards, J. Konishi and D. Wallinger. 1976. Guideline to collecting cones of B.C. conifers. B.C. For. Serv./Can. For. Serv., Joint Rep. No. 3, 98p.
Edwards, G. 1962. The germination requirements of Abies species. Proc. Internat. Seed Testing Assoc. 27: 127–210.
Edwards, D.G.W. 1969. Investigations on the delayed germination of noble fir. Dissert. Abstr. Internat. 30/06 B: 2482.
Edwards, D.G.W. 1970. Book review of “The New Forest: an ecological history” by Colin R. Tubbs. David & Charles: Newton Abbot, 248p. Forest History 14(1): 35–36.
Edwards, D.G.W. 1970. Moisture relations during stratification of noble fir seed. Abstracts, First North Am. For Biol. Workshop, Mich. State Univ., August 1970. (Pages unnumbered).
Edwards, D.G.W. 1971. The kinetics of water absorption in stratifying and non-stratifying noble fir (Abies procera Rehd.) seeds. Can. J. For. Res. 1(4): 235–240.
Edwards, D.G.W. 1971. An aberrant cone in western hemlock. Canada Dept. Environ., Bi-Mon. Res. Notes 27(5): 33.
Edwards, D.G.W. 1973. Effects of stratification on western hemlock germination. Can. J. For. Res. 3(4): 522–527.
Edwards, D.G.W. 1973. Effect of a soil wetting agent on germination of four important British Columbia conifers. Forest. Chron. 49(3): 1–4.
Edwards, D.G.W. 1973. Polaroid film for rapid seed radiography. International Symposium on Seed Processing, IUFRO WP, Bergen, Norway. Vol. 1—Paper No. 6. 8p.
Edwards, D.G.W. 1974. A germination dish for testing tree seeds. Dep. Environment, Can. Forest. Serv., Bi-Mon. Res. Notes 30(4): 26–27.
Edwards, D.G.W. 1974. More on radiographs. Tree Planters’ Notes 25(2): 21.
Edwards, D.G.W. 1975. Abnormal germinants of western hemlock. Seed Sci. and Technol. 5: 799–803.
Edwards, D.G.W. 1975. Propagation of yellow cedar. “High elevation reforestation problems.” Interim Research Results No.1, B.C.F.S./C.F.S. Joint Report: 4.
Edwards, D.G. 1976. Seed physiology and germination in western hemlock. Pages 87–102 in Atkinson, W.A. and R.J. Zasoski (eds). Proc. Western Hemlock Management Conference, May 1976, Alderbrook, Washington. College of Forest Resources, University of Washington. 317p.
Edwards, D.G.W. 1976. World Directory of tree seed workers. Pub. by Can. For. Serv. for IUFRO, 133p.
Edwards, D.G.W. 1977. Tree seed research, Pacific Forest Research Centre, B.C. Proc. 16th.Meeting Canad. Tree Imp. Assoc., Part I: 209–216.
Edwards, D.G.W. 1979. An improved air seed-sorter for laboratory use. Dep. Environ., Can. For. Serv., Pac. For. Res. Cent., Victoria, B.C. BC-X-188, 11p.
Edwards, D.G.W. 1979. Maturity and Seed Quality: a state-of-the-art review. Pages 233–263 in F.T. Bonner (ed.). Proc. USFS/IUFRO/Miss. St. Univ., Intern. Sympos. “Flowering and seed development in trees.” May 1978. Starkville, Miss. U.S. For. Serv., Southern For. Exp. Sta., Starkville, Miss. 380p.
Edwards, D.G.W. 1979. Tree seed research, Pacific Forest Research Centre, B.C., 1977–1979. Proc. 17th Meeting Can. Tree Imp. Assoc., Part I: 231–236.
Edwards, D.G.W. 1980. A new pre-chilling method for true fir seeds. Proc. Joint Mtg. Intermountain Nurseryman’s Assoc. and Western Forest Nursery Assoc., Boise, Idaho, Aug. 1980: 58–65.
Edwards, D.G.W. 1980. Maturity and quality of tree seeds—a state-of-the-art review. Seed Sci. and Technol. 8: 625–657.
Edwards, D.G.W. 1980. Progress report of the Working Group on germination of other seeds. Rep. to For. Tree Comm., Internat. Seed Testing Assoc., 19th Congr., Vienna, Austria, 1980. Seed Sci. and Technol. 9(l): l90–l9l.
Edwards, D.G.W. 1980. The Western Forest Tree Seed Council. Proc. Joint Mtg. Intermountain Nurseryman’s Assoc. and Western Forest Nursery Assoc. Boise, Idaho Aug. 1980: 29–31.
Edwards, D.G.W. 1980. Sampling and purity testing. Pages 37–113, Proc. IUFRO/ISTA/INIF Int. Workshop on Tropical Seed Problems, Mexico, 1980. Instituto Nacional de Investigationes Forestales, SARH. 352p.
Edwards, D.G.W. 1981a. Cone collection and processing effects on seed quality and yield. Pages 12–37 in R.F. Huber (comp.). Proc. Seed Workshop on High Quality Collection and Production of Conifer Seed. Can. For. Serv., Edmonton, 1979. 88p.
Edwards, D.G.W. 1981b. Impact of seed quality on costs of nursery stock. Pages 79–83 in R.F. Huber (comp.). Proc. Seed Workshop on High Quality Collection and Production of Conifer Seed. Can. For. Serv., Edmonton, 1979. 88p.
Edwards, D.G.W. 1982. Storage of pre-chilled Abies seeds. Pages 195–203 in B.S.P. Wang and J.A. Pitel (comp. and eds.). “Seed storage.” Proc. IUFRO WP S2.01.06 Intern. Sympos., Petawawa Nat. For. Inst. Sept. 1980. Can. For. Serv., Min. Supply and Serv., Ottawa. 243p.
Edwards, D.G.W. 1982. Collection, processing, testing and storage of true fir seeds—a review. Pages 113–137. IN: C.D. Oliver and R.M. Kenady (eds.). Proc. True Fir Symposium, Biology and Management in the Pacific Northwest, Seattle, Feb. 1981. US For. Serv., Pac. Northwest and Range Exp. Sta. and Univ. Wash., Coll. For. Resources.
Edwards, D.G.W. l982. Improving seed germination in Abies. Proc. Internat. Plant Propagators’ Soc. Mtg., Richmond, B.C., Canada, l98l: 69–78.
Edwards, D.G.W. l983. Role of the Pacific Forest Research Centre in testing tree seeds under international rules. For. Chron. 59: 67–69.
Edwards, D.G.W. 1984. The role of seeds and seed research in combating the exploitation of the world’s forest resources. Seed Sci. and Technol. 12: 757–765.
Edwards, D.G.W. 1985. Cone prediction, collection and processing. IN: Proc. Conifer Tree Seed in the Inland Mountain West, Symposium, Missoula, MT. U.S. Dep. Agric. For. Serv. Rep. INT-203.
Edwards, D.G.W. 1985. Seed Vac. In, ISTA Handbook for home-made equipment for seed testing (E. Madsen, ed.). Internat. Seed Test. Assoc. Zurich: 171–173.
Edwards, D.G.W. 1985. An improved air seed cleaner/sorter. In, ISTA Handbook for home-made equipment for seed testing (E. Madsen, ed.). Internat. Seed Test. Assoc., Zurich: 44–46.
Edwards, D.G.W. 1986. Special pre-chilling techniques for tree seeds. J. Seed Technol. 10: 151–171.
Edwards, D.G.W. 1986. Cone prediction, collection and processing. Pages 78–102 in R.C. Shearer (comp.). Proc. Sympos. “Conifer tree seed in the Inland Mountain West.” Aug. 1985. Missoula, Montana, USA. U.S. For. Serv., Gen. Tech. Rep. INT-203.
Edwards, D.G.W. 1987. Methods and procedures for testing tree seeds in Canada. Can. For. Serv., For. Tech. Rep. 36 (bilingual), 31p.
Edwards, D.G.W. 1988. Forest tree seed certification in Canada under the OECD scheme and ISTA rules: 1981–1985. Can. For. Serv., Info. Rep. BC-X-299, 16p.
Edwards, D.G.W. (comp. and ed.). 1993. Dormancy and barriers to germination. Proc. Internat. Sympos. IUFRO Project Group P2.04-00 (Seed Problems). April 1991, Victoria, B.C., Canada. Can. For. Serv., Pacific Forestry Centre. 153p.
Edwards, D.G.W. 1993. An historical overview of seed upgrading techniques and on to new roads of discovery. Pages 21–24 IN: F.T. Portlock (comp.). Proc. Joint Mtg. B.C. Seed Dealers’ Assoc./West. For. Range Seed Counc. June 1993. Vernon, B.C. For. Canada/BC Min. For. 53p.
Edwards, D.G.W. 1997. The stratification-redry method with special reference to true fir seeds. Pages 172–182. IN: T. Landis (ed.). National Proc.: Forest and Conserv. Nurs. Assocs. Mtg., Salem, Oregon; August 1996. USDA For. Serv. Gen. Tech. Rep. PNW-GTR-389.
Edwards, D.G.W. 1999. Two newer methods for improving physical quality of forest seeds. Pages 165–182. IN: Edwards D.G.W. and S.C. Naithani (eds.). Seed and nursery technology of forest trees. New Age International (P) Ltd., Publishers. New Delhi, India. 309p.
Edwards, D.G.W. 2000. Forest tree seeds at the end of the
20th. Century: major accomplishments and needs. A
State of the Knowledge Report on forest tree seeds, prepared
for the International Union of Forestry Research Organizations
(IUFRO) XXI World Congress, Kuala Lumpur, Malaysia. 10p. Full
text can be accessed at:
Edwards, D.G.W. 2002. Seed-to-wing attachments in important members of the Pinaceae, with additional observations on members of the Cupressaceae. IN: Thanos, C.A., Beardmore, T., Connor K., Tolentino, I., eds. Proceedings IUFRO Research Group 2.09.00 (Seed Physiology and Technology) International Symposium, “Tree Seeds 2002,” Chania, Crete; Sept. 11–15, 2002; Univ. Athens, MAICh, Hellenistic Ministry of Agriculture, International Soc. for Seed Science; 59–69.
Edwards, D.G.W. 2008. Abies P. Mill. fir. Pages 149–198. IN: Bonner, F.T., R.P. Karrfalt and R. Nisley. The Woody Plant Seed Manual. United States Dept. Agric., For. Serv., Agric. Handbk. 727. 1223p.
Edwards, D.G.W. and Y.A. El-Kassaby. 1988. Effect of flowering phenology, date of cone collection, cone-storage treatment and seed pretreatment on yield and germination of seeds from a Douglas-fir seed orchard. J. For. Ecol. and Manag. 25: 17–29.
Edwards, D.G.W. and Y.A. El-Kassaby. 1993. Ex-situ conservation of forest biodiversity in British Columbia. Pages 65–67. IN: V. Marshall (comp.). Proc. For. Ecosystem Dynamics Workshop. February 1993. Pac. For. Cent., Victoria, BC. Can./Brit. Columbia. Partnership Agreement on For. Res. and Dev: FRDA II. FRDA Rep. 210. 98p.
Edwards, D.G.W. and Y.A. El-Kassaby. 1995. Douglas-fir genotypic response to seed stratification. Seed Sci. & Technol. 23: 771–778.
Edwards, D.G.W. and Y.A. El-Kassaby. 1996. The effect of stratification and artificial light on the germination of mountain hemlock seeds. Seed Sci. & Technol. 24: 225–235.
Edwards, D.G.W. and Y.A. El-Kassaby. 1996. The biology and management of coniferous forest seeds: genetic perspectives. Forest. Chron. 72: 481–484.
Edwards, D.G.W. and C.L. Leadem. 1988. The reproductive biology of western red cedar with some observations on nursery production and prospects for seed orchards. Proc. Conf. “Western red cedar—does it have a future?” Univ. Brit. Columbia., July 1987: 102–113.
Edwards D.G.W. and M.D. Meagher. 1995. Mountain hemlock (Tsuga mertensiana [Bong.] Carr.)—an annotated bibliography. Can. For. Serv., Pac. For. Cent., Victoria, BC. Info. Rep. BC-X-352. 45p.
Edwards, D.G.W., M.D. Meagher and Y.A. El-Kassaby. 1993. Genetic diversity in mountain hemlock (Tsuga mertensiana [Bong.] Carr. Pages 68–71 in V. Marshall (comp.). Proc. For. Ecosystem Dynamics Workshop. Feb. 1993. Pac. For. Cent., Victoria, BC. Can./Brit. Columb. Partnership Agreement on For. Res. Dev: FRDA II. FRDA Rep. 210. 98p.
Edwards, D.G.W., G.E. Miller, F.T. Portlock and J.R. Sutherland. l984. Tree Seed Research and Certification, Pacific Forest Research Centre l98l-82. Proc. l9th Meeting Canad. Tree Imp. Assoc., Part I: 210–215.
Edwards, D.G.W., G.E. Miller, F.T. Portlock and J.R. Sutherland. 1986. Cone and seed research and seed certification, Pacific Forestry Centre 1983–1984. Proc. 20th Meeting Can. Tree Imp. Assoc. Part I: 219–224.
Edwards, D.G., S. Eis, G.E. Miller, F.T. Portlock, J.R. Sutherland and D.W. Taylor.1988. Cone and seed research and seed certification, Pacific Forestry Centre 1985–86. Proc. 21st. Meeting Canad. Tree Imp. Assoc. Part I: 127–131.
Edwards, D.G.W. and A.K. Mitchell. 1993. Conserving genetic resources of forests in the Pacific and Yukon Region: an introduction to Project PC-71-50. Pages 63–64. IN: V. Marshall (comp.). Proc. For. Ecosystem Dynamics Workshop. Feb. 1993. Pac. For. Cent., Victoria, B.C. Can./Brit. Columb. Partnership Agreement on For. Res. and Dev.: FRDA II. FRDA Rep. 210. 98p.
Edwards, D.G.W. and P.E. Olsen. 1972. R-55 rodent repellent: effect on germination in Douglas-fir and western hemlock. Can. J. For. Res. 2(3): 256–263.
Edwards, D.G.W. and P.E. Olsen. 1973. A photoperiod response in germination of western hemlock seeds. Can. J. For. Res. 3(1): 146–148.
Edwards, D.G.W., Pollard, D.F.W. and B.S.P Wang. 1988. Guidelines for grading and labeling forest tree seeds in Canada. For. Chron. 64: 334–344.
Edwards, D.G.W. and F.T. Portlock. 1985. Certification of lodgepole pine seeds of Canadian origins under the OECD scheme. Page 374, IN: Baumgartner, D.M., R.G. Krebill, J.T. Arnott and G.F. Weetman, comp. and eds.). Proc. Sympos. “Lodgepole pine, the species and its management.” May 1984. Univ. Brit. Columbia, Wash. St. Univ. Coop. Extension. 381p.
Edwards, D.G.W. and F.T. Portlock. 1986. Expansion of Canadian tree seed certification. For. Chron. 62:461–466.
Edwards, D.G.W. and F.T. Portlock. 1993. Forest tree seed certification in Canada. Pages 21–127, IN: H. Wolf (ed.). Seed procurement and legal regulations for forest reproductive material in tropical and subtropical countries. Proc. IUFRO WP S2.02.21 First Internat. Sympos. Nairobi, Kenya. October 1992. GTZ-Forestry Seed Centre Muguga, Nairobi, Kenya.
Edwards, D.G.W., F.T. Portlock and D.W. Taylor. l983. The “Seed-Vac,” a homemade device for transferring seed samples. Canada Dept. of Environment, Can.. For.. Serv. Research Notes 3(4): 22–24.
Edwards, D.G.W. and J.R. Sutherland. 1979. Hydrogen peroxide treatments of Abies seeds. Dep. Environ., Can. For.. Serv., Bi-Mon. Res. Notes 35(1): 3–4.
Edwards, D.G.W., J.R. Sutherland and G.E. Miller. l982. Tree Seed Research, Pacific Forest Research Centre l979-l980. Proc. l8th Meeting Canad. Tree Imp. Assoc., Part I: 69–73.
Edwards, D.G.W. and D.W. Taylor. 1985. Germination of commercially-collected lodgepole pine seeds from British Columbia and the Yukon Territory. Page 375, IN: D.M. Baumgartner, G. Krebill, J.T. Arnott and G.F. Weetman (comp. and eds.). Proc. Sympos. “Lodgepole pine, the species and its management.” May 1984. Univ. Brit. Columb. Wash. State Univ. Coop. Extension. 381p.
Edwards, D.G.W., Taylor, D.W. and E.C. McKendry. 1985. Enhancing seed lot quality in lodgepole pine by flotation sorting. Pages 375–376, IN: D.M. Baumgartner, D.M., R.G. Krebill, J.T. Arnott and F.G. Weetman (comp. and eds.). Proc. Sympos. “Lodgepole pine, the species and its management.” May 1984. Univ. Brit. Columb. Wash. St. Univ. Coop. Extension. 381p.
Edwards, D.G.W. and B.S.P. Wang. 1995. A training guide for laboratory analysis of forest tree seeds. Nat. Res. Can., Can. For. Serv., Pacific and Yukon Region, Info Rep. BC-X-356, 64p.
Edwards, D.G.W., B.S.P. Wang et P.A. Boross. 1994. Guide des essais de semences forestières en laboratoire. Res. Nat. Can., Serv. Can. For., Inst. For. Nat. Petawawa, Rap. d’Info. PI-X-110F, 57p.
El-Kassaby, Y.A., A. Benowicz, and D.G.W. Edwards. 2001. Genetic variation in germination attributes and response to accelerated aging in western hemlock seeds. Submitted to For. Ecol. and Manag.
El-Kassaby, Y.A., K. Chaisurisri, D.G.W. Edwards, and D.W. Taylor. 1993. Genetic control of germination parameters of Douglas-fir, Sitka spruce, western redcedar, and yellow-cedar and its impact on container nursery production. Pages 37–42, IN: D.G.W. Edwards, comp. and ed. Proc. IUFRO Sympos. “Dormancy and barriers to germination,” Victoria, BC, Canada. April 1991. For. Can., Pac. For. Cent. 153p.
El-Kassaby Y.A. and D.G.W. Edwards. 1998. Genetic control of germination and the effects of accelerated aging in mountain hemlock seeds and its relevance to gene conservation. For. Ecol. and Manag. 112: 203–211.
El-Kassaby Y.A. and D.G.W. Edwards. 2001. Germination ecology of mountain hemlock (Tsuga mertensiana [Bong.] Carr.). For. Ecol. and Manag. 144: 183–188.
El-Kassaby, Y.A. D.G. Edwards and C. Cook. 1990. Impact of crop management practices on seed yield in a Douglas-fir seed orchard. Silvae Genet. 39: 226–230.
El-Kassaby, Y.A., D.G.W. Edwards and D.W. Taylor. 1990. Effect of water-spray cooling treatment in a Douglas-fir seed orchard on seed germination. New Forests 4: 137–146.
El-Kassaby, Y.A., D.G.W. Edwards and D.W. Taylor. 1992. Genetic control of germination parameters in Douglas-fir and its importance for domestication. Silvae Genet. 41: 48–54.
Eremko, R.D., D.G.W. Edwards and D. Wallinger, 1989. A guide to collecting cones of British Columbia conifers. Canada/Brit. Columbia For. Resource Development Agreement (FRDA) Rep. 055, 114p.
Gordon, A.G. and D.G.W. Edwards. 1991. Testing the germination of tree seeds. Chapter 5 in A.G. Gordon, P. Gosling and B.S.P. Wang (eds.). Tree and shrub seed handbook. Internat. Seed Test. Assoc., Zurich, Switzerland. (Pages numbered by chapters.)
Leadem, C.L. and D.G.W. Edwards. 1984. A multiple-compartment tree seed tumbler-drier. Tree Plant. Notes 35(3): 23–25.
Pollard, D.F.W., D.G. Edwards and C.W. Yeatman (eds). 1982. Seed orchard strategies for tree improvement. Proc. 18th. Meeting Canad. Tree Imp. Assoc. Part II: 1–194.
Sutherland, J.R. and D.G.W. Edwards. 1976. Pigments for use on conifer seeds sown in forest nurseries. Can. For. Serv, Rep. BC-X-146, 12p.
Sweeney, J.D., Y.A. El-Kassaby, D.W. Taylor, D.G.W. Edwards and G.E. Miller. 1991. Applying the IDS method to remove seeds infested with the seed chalcid, Megastigmus spermotrophus Wachtl., in Douglas-fir, Pseudotsuga >menziesii (Mirb.) Franco. New Forests 5: 327–334.
Tanaka, Y. and D.G.W. Edwards. 1986. An improved and more versatile method for pre-chilling Abies procera Rehd. seeds. Seed Sci. and Technol. 14: 457–464.
Auclair, A.N.D., D.G.W. Edwards (and others). 1984. Scoping issues and research problems: forest renewal, stand tending and resource inventory in British Columbia. Canada, Pac. For. Res. Cent. Misc. Pub. 126. 73p.
Edwards, D.G.W. 1974. Seed treatment. IN: Western Hemlock Regeneration, a synthesis of current research and knowledge: 2–4. Hemlock Regeneration Workshop, Weyerhaeuser Co. For. Res. Cent., Centralia, WA.
Edwards, D.G.W. 1974. Root growth and regeneration. IN: Western Hemlock Regeneration, a synthesis of current research and knowledge: 10–12. Hemlock Regeneration Workshop, Weyerhaeuser Co. For. Res. Cent., Centralia, WA.
Edwards, D.G.W. l978. Photoperiod and germination: a review. Presented at BCFS Reforestation/Research Div. Tech. Mtg, Jan. l978. 4p.
Edwards, D.G.W. l979. Collection, processing, storage and testing of Abies seed: a state-of-the-art review. Paper presented at the True Fir Management Cooperative Symposium on Regeneration and Management of Young True Fir Stands, Redding, Calif. May l979. 43p.
Edwards, D.G.W. 1984. (Chairman). B.C. Ministry of Forests/Canadian Forestry Service Joint Cone and Seed Committee, Cone and seed research needs and priorities. Report presented to the Joint Cone and Seed Comm. Management Steering Comm. 9p.
Edwards, D.G.W. 1985. Forest Tree Seed Certification under the OECD scheme in Canada 1984–1985. Report presented at the 1985 Meeting of OECD Designated Authorities, Paris, France. 5p. plus appendix.
Edwards, D.G.W. 1985. Operation of the OECD scheme in Canada. Report presented at the 1985 Meeting of OECD Designated Authorities, Paris France. 4p.
Edwards, D.G. 1986. Report on seed drying tests made at Pine Ridge Seed Processing Centre, Alberta, April 1986. June 1986. 14p.
Edwards, D.G.W. 1986. EEC import restriction of tree seeds. Briefing Note for the Associate Deputy Minister, Dept. of Agriculture. Pacific Forest. Cent., Nov. 1986. 2p.
Edwards, D.G.W. 1987. Progress Report—Western white pine germination research. Report presented to the Western Forest and Range Council Meeting, Langley, B.C. March 1987. 9p.
Edwards, D.G.W. 1987. Forest Tree Seed Certification under the OECD scheme in Canada 1986–1987. Report presented at the 1987 Meeting of OECD Designated Authorities, Paris, France. 3p.
Edwards, D.G.W. 1989. Forest Tree Seed Certification under the OECD scheme in Canada 1988–1989. Report presented at the 1989 meeting of OECD Designated Authorities, Paris, France. 3p.
Edwards, D.G.W. 1989. Report on Seed Technology Training Course, National Institute of Agricultural Botany, Cambridge, England, July 1989. 5p.
Edwards, D.G.W. Report on the First Annual Garry Oak Ecosystems Recovery Team Research Colloquium; Pacific Forestry Centre (PFC), Victoria; March 28, 2003.
Edwards, D.G. and D.W. Taylor. 1988. Report on seed drying tests made at Surrey Seed Centre, BC, March 1987. Mar 1988. 10p. (plus appendix).
Pollard, D.F.W. and D.G.W. Edwards. 1981. Seeds Act of Canada: Reasons for forest tree seeds regulations. To accompany Draft 3 of Proposed Forest Tree Seeds Regulations, circulated Canada-wide. 1p.
Pollard, D.F.W., D.G.W. Edwards and B.S.P. Wang. l98l. Canada Seeds Act: Forest Tree Seeds Regulations and Schedules. Four drafts developed in collaboration with Petawawa Nat. For. Instit. Draft l June l980, l0p.; draft 2, Aug l980, l0p.; draft Schedule A, Oct. l980, l6p.; draft 3, Jan l98l, 9p.; draft 4, Sept. 1982; draft 5, June 1984; draft 6, July 1985.
Edwards, D.G.W. 1977. Separation of Abies seeds by flotation. Proc. Assoc. Offic. Seed Analysts/Soc. Commerc. Seed Technologists Ann. Mtg. Amherst, Mass. 6p.
Edwards, D.G.W. 1977. Upgrading seedlots and other work in progress at the Canadian Forestry Service, Pacific Forest Research Centre. West. For. Tree Seed Counc. Ann. Mtg. Portland, Oregon. 11p.
Edwards, D.G.W. 1978. Germination after redrying stratified Abies seeds. West. For. Tree Seed Counc. Ann. Mtg. Corvallis, Oregon. 4p.
Edwards, D.G.W. 1982. Tree seed sampling. West. For. Tree Seed Counc. Workshop. Tacoma, Wash. 3p.
Edwards, D.G.W. 1984. The IDS seed sorting process. West. For. and Range Seed Counc. Ann. Mtg. Portland, Or: 5p.
Edwards, D.G.W. 1984. Upgrading conifer seedlots by means of the IDS flotation-separation method. Assoc. Offic. Seed Analysts/Soc. Commerc. Seed Technologists Ann. Mtg. Boise, Idaho 9p.
Edwards, D.G.W. 1985. Special pre-chilling techniques for tree seeds. Assoc. Offic. Seed Analysts/Soc. Commerc. Seed Technologists Sympos. “Major seed problems in forestry,” Virginia. 15p. plus slides. (Invited presentation).
Edwards, D.G.W. 1985. Use of the IDS seed sorting method on BC conifers. Brit. Columbia Nurseryman’s Ann. Mtg. Duncan, B.C.. 4p.
Edwards, D.G.W. 1985. Seed research update. West. For. and Range Seed Counc. Ann. Mtg. Portland, Oregon. 3p.
Edwards, D.G.W. 1985. Proposals for changes to the AOSA Seed Testing Rules. Submitted to Assoc. Offic. Seed Analysts/Soc. Commerc. Seed Technologists Ann. Mtg., Davis, Ca. 11p.
Edwards, D,G,W. 1986. Effect of compound stratification on the germination of western white pine. Assoc. Offic. Seed Analysts/Soc. Commerc. Seed Technologists Ann. Mtg. Minneapolis, Minn. 7p.
Edwards, D.G.W. 1987. Current seed research in Canada. Invited Seminar, Dept. Forest Genetics, Swedish University of Agricultural Sciences, Umea, Sweden.
Edwards, D.G.W. 1988. Proposals for changing the Purity Test for conifer seeds. Submitted to Internat. Seed Test. Assoc. For. Tree and Shrub Seed Comm. Workshop. Macon, Ga. 6p.
Edwards, D.G.W. 1988. Observations on Table 6A (Procedures for tetrazolium tests) and Preparation and Evaluation Guides. Submitted to ISTA-FTSSC Workshop, Macon, Ga. 6p.
Edwards, D.G.W. 2002. Breaking dormancy in tree seeds with special reference to firs (Abies species)-the 1.4x solution. 44th Annual Horticulture Growers’ Short Course, together with the Pacific Agriculture Show; February 7–9, 2002; TRADEX, Abbotsford, British Columbia.
Edwards, D.G.W. 2002. Proposal to update the World Directory of Tree Seed Workers. Presented at the IUFRO Research Group 2.09.00 (Seed Physiology and Technology) International Symposium, “Tree Seeds 2002,” Chania, Crete; Sept. 11–15, 2002.
Edwards, D.G.W. 2002. Proposal to create a Global Bibliography of Tree Seeds. Presented at the IUFRO Research Group 2.09.00 (Seed Physiology and Technology) International Symposium, “Tree Seeds 2002,” Chania, Crete; Sept. 11–15, 2002.
Edwards, D.G.W. 2002. Seed-to-wing attachments in important members of the Pinaceae with additional observations on members of the Cupressaceae and Taxodiaceae. PowerPoint presentation, IUFRO International Symposium “Seed 2002,” Sept. 11–15, 2002, Chania, Crete.
Edwards, D.G.W. 2006. Reasons for revising pure seed definitions for important coniferous species—Pinaceae, Cupressaceae, Taxaceae, Taxodiaceae. PowerPoint presentation, ISTA For. Tree and Shrub Seed Comm. Seminar, Sept. 12–15, 2006, Verona, Italy.
Edwards, D.G.W. 2003. Breaking dormancy in tree seeds with special reference to firs (Abies species)—the 1.4x solution. Sixth Biennial Exotic Conifer Conference and Field Day; September 9–10, 2003; Clinton, Iowa and Fulton, Illinois.
Edwards, D.G.W. 2003. Breaking dormancy in tree seeds with special reference to firs (Abies species)—the 1.4x solution. Sixth International Christmas Tree Research and Extension Conference; September 14–19, 2003; Hendersonville and Boone, North Carolina.
Edwards D.G.W., Y.A. El-Kassaby and M.D. Meagher. Biology and genetics of Garry oak (Quercus garryana). Presented at the International Garry Oak Symposium; University of Victoria; Victoria, British Columbia; May 1999.
Edwards, D.G.W. and C.L. Leadem. 1995. The effect of temperature cycling on germination in four conifers. Paper presented at the IUFRO XX World Congress, Tampere, Finland, Aug. 95. 12p.
Pollard, D.F.W. and D.G.W. Edwards. 1981. Outline of cone and seed studies conducted at the Pacific Forest Research Centre. Can. For. Serv. Workshop on Cone and Seed Research, Pac. For. Res. Cent., Victoria.
free from the presence of any other substances; free from contamination or admixture; unalloyed.
(Cayne and Lechner, 1987).
free from anything of a different, inferior or contaminating kind; free from extraneous matter; unmodified by an admixture.
(Stein and Urdang, 1967).
free from admixture or anything debasing or deteriorating; unadulterated; uncorrupted; uncontaminated; conforming accurately to a standard of quality or style; faultless; the genuine article.
unmixed with any other thing; free from admixture; containing no added, substitute or foreign substance; free from what harms, vitiates, weakens, or pollutes; containing nothing that does not properly belong; free from alteration, error or foreign increment; without admixture.
incapable of moving, acting or resisting an opposing force; hard to get to move or act; inactive.
(Cayne and Lechner, 1987).
having no inherent power of action, motion or resistance; inactive or sluggish by nature; immobile, unmoving, motionless, lifeless.
(Stein and Urdang, 1967).
having no inherent power of action, movement, inactive, inanimate.
unskilled; idle; motionless; not having the power to move itself; not having or manifesting active properties; lifeless; sluggish; indolent.
sticking in, fixed, situated, contained in something, existing in something as a permanent attribute, a characteristic or essential element of something.
having no organic life; showing no sign of having life.
(Cayne and Lechner, 1987).
not animate; lifeless; inactive; dormant; inert; dead.
(Stein and Urdang, 1967).
(Cayne and Lechner, 1987).
alive; able to move voluntarily.
(Stein and Urdang, 1967).
Like all other products, whether natural or man-made, seeds are a commodity to be sold on a special market. So imagine seeing a pair of advertisements by a forest tree seed dealer who has the remnants of a seedlot of your favourite species (perhaps Pseudotsuga menziesii, Pinus sylvestris, Picea abies…?) that was collected some 3 years ago for a research project. The seeds have been in dry-cold storage (6–8% mc, -17°C) ever since. Some damage occurred during seed processing, but the broken seeds have been meticulously sorted and removed from the intact seeds. The seed dealer says he can guarantee that all pieces of seeds are more than one-half the original size—any smaller pieces have been discarded. He is offering two containers of these seeds: one contains only pure intact seeds—no pieces—while the second container contains exactly the same number of seeds (at least 1,000), that are pure seeds according to ISTA Rule 184.108.40.206.2, in that they are all larger than one-half their original size, and they still have a corresponding portion of their seed coat attached. He tells you that the original germination test (before storage) was 98.5%, obviously on intact seeds. The price on both containers is very good. Container A contains 1,000 (minimum) intact seeds for $250.00. Container B contains 1,000 (minimum) pieces of seed larger than one-half their original size for $140.00 (more than one half the price of intact seeds). So which container would you be inclined to purchase?
My warmest and affectionate thanks go to Mr. Ewan R.A. Edwards (Victoria, BC) for his brilliance in spotting the many textual inconsistencies, for coping with the reviewer’s whining when changes opened up new possibilities, for his extraordinary patience while the text was tyepset and corrected, typeset and corercted, typeset and corrected, and his expertise in design and layout.
Sincere thanks to Dr. Eleanor E. White (Shawnigan Lake, BC) for the beam balance insight, and listening to the many arguments between the reviewer and himself.
Also to Dr. Lorne Hammond, Royal British Columbia Museum (Victoria, BC), for photographs of the beam balance and weights.
This review would not have been possible without the early support during proposals for PSD revisions, of Dr. Zdenka Prochazkova, Czech Republic, former Chair of the ISTA Forest Tree and Shrub Seed Committee.