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Seed-to-wing attachments in important members of the Pinaceae, with additional observations on members of the Cupressaceae and Taxaceae

D.G.W. EDWARDS

Paper presented at IUFRO Research Group 2.09.00 (Seed Physiology and Technology) International Symposium, "Tree Seeds 2002", Chania, Crete, September 11-15, 2002.

Abstract

Wings of seeds of spruce and many pine species can be removed easily in toto because they are not fused to the seed coat. However, confusion has arisen regarding what constitutes "pure seeds" (when testing for trading purposes) in several other genera. A photographic survey of wing-to-seed attachments demonstrated that certain genera, and certain species within a given genus, should be separated when "pure seeds" are defined. Proposals for revising international pure seed definitions are discussed.

Keywords

Abies, Calocedrus, Cedrus, Chamaecyparis, Cupressus, Keteleéria, Larix, Picea, Pinus, Pseudotsuga, Sequoiadendron, Thuja, Tsuga, integument, pure seeds, seedwing

Introduction

Mature seeds of most coniferous trees bear one or more membranous wings; notable exceptions include certain pines, such as Pinus albicaulis, P. cembra, P. flexilis, P. koraiensis, as well as Taxodium distichum, in which wings are rudimentary or absent. When shed from the parent tree, wings allow air currents to carry them some distance away. For artificial reforestation programs, the same wings are an impediment to sowing, and winged-seeds on the surface of a growing medium are easily disturbed by air movement. Typically, wings and seeds are separated before storage since wing removal greatly reduces the seed bulk. Modern sowing machinery relies on clean, wingless seeds for greatest efficiency. Seeds of the Cupressaceae typically bear more than one wing that are difficult to remove without damaging the seeds, so these seeds are left intact.

When traded, tree seed containers typically indicate the pure seed percentage, an indication of how "clean" is the lot with regard to the species being marketed, seeds of any other species, and any inert matter. Inert matter includes seeds from which the seedcoats have been entirely removed, broken or damaged seeds, cone scales, wings, bark, etc., and the analyst must be able to recognize and separate these components. As an aid in this, a series of "pure seed definitions" have been provided by the International Seed Testing Association (ISTA 1999); the companion Handbook of Pure Seed Definitions with illustrations (Felfoldi 1987) excludes forest tree seeds. Similar descriptions, including tree seeds, have been provided by the Association of Official Seed Analysts (of North America) (AOSA 1998). All are aimed at standardizing what are to be classified as pure seeds, and periodically they revised. The focus here will be on the ISTA (1999) rules.

Of the 63 Pure Seed Definitions (PSDs) included in the International Seed Testing Rules (ISTA 1999: 133-144), 5, viz., PSD 10, 47, 49, 50 and 51, cover conifer species; the complete list of PSD numbers by genus and family can be found on pages 123-132. The vast majority of coniferous genera are covered currently in 3 PSDs as follows:

Due to space limitations of the published Proceedings, the main focus of this report was limited to PSD 51, the text of which states that a pure seed is a:

"seed, without wing, with (but occasionally without) integument, provided a portion of the testa is attached. Piece of seed larger than one-half the original size, without wing or integument, provided a portion of the testa is attached."

PSD 51 then goes on to describe that "integument":

"refers to the tissue attaching the wing to the seed. In Pinaceae with this definition, the integument is fused to the seed, is rarely removed in processing, and is impossible to consistently remove, without causing damage. Hence, seed with integument attached is considered to be 'pure seed'. Winged seed - i.e. seed with an integument plus wing still attached must be weighed and reported as a separate percentage from 'pure seed' according to paragraphs 3.5.2.A.9 and 3.7. After weighing, the winged seed and pure seed fractions should be recombined and used in representative portions for counting out the germination replicates."

Note that this use of the term "integument" differs from the strict, botanical definition which is variously given as "the tissues covering or surrounding the ovule, usually consisting of an inner and outer layer which comprises the seedcoat of the mature ovule" (Copeland 1976), or "the one or two layers of tissue, often fused, that enclose the nucellus of an ovule and that develop after fertilization into seed coats" (Bonner 1984). In conifers, the seed coat forms even when the ovule is not fertilized.

The objective of the study reported here was to review the current PSDs mentioned above, with the focus on PSD 51, to determine if species' assignments were appropriate. Seed features to which PSDs referred, particularly attachments of wings to the seeds, were recorded on macrophotographs.

Materials and Methods

Seeds of 39 species in 13 genera (Table 1) from the reference collection at the Pacific Forestry Centre (Canadian Forest Service), Victoria, British Columbia, were examined, and photographed using 35-mm colour-transparency film (ASA 200). For larger seeds, a camera fitted with a 28-85 mm AF lens (macro setting) combined, as required, with a 12 mm extension ring and ring flash was used; to highlight special features, the ring flash was supplemented occasionally with a fibre optic light source. For intermediate and very small seeds, or for very close detail, dissecting microscopes equipped with 35-mm cameras, a ring lamp, or one or more fibre optic lamps, were employed. Computer images were obtained using a slide scanner at maximum (2700 dpi) resolution.

Results and Discussion


Figure 1

Figure 1
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Abaxial view of Abies numidica seeds. A - seed with entire wing and integument showing flaps. B - naked seed. C - undamaged integument (wing broken off) from which seed B was removed.


Figure 2

Figure 2
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Abaxial view of Abies alba seeds. A - seed with integument (wing broken off), a "pure seed" according to PSD 51. B - naked seed. C - undamaged integument from which seed B was removed.


Figure 3

Figure 3
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Abaxial view of Abies amabilis seeds. A - seed with entire wing and integument showing flaps. B - seed with integument (wing broken off), a "pure seed" according to PSD 51. C - naked seed. D - intact wing and integument from which seed C was removed.


Figure 4

Figure 4
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Abaxial view of Abies procera seeds. A - seed with integument (wing broken off), a "pure seed" according to PSD 51. B - naked seed. C - undamaged integument from which seed B was removed.


Figure 5

Figure 5
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Abaxial view of Abies nordmanniana seeds. A - seed with integument (wing broken off), a "pure seed" according to PSD 51. B - naked seed. C - undamaged integument from which seed B was removed.


Figure 6

Figure 6
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Abaxial view of an Abies sibirica seed with integument (wing broken off). This is a "pure seed" according to PSD 51.


Figure 7

Figure 7
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Abaxial view of the "empty" undamaged integument from which the Abies sibirica seed in Figure 6 was removed.


Figure 8

Figure 8
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A naked Abies numidica seed. The glossy area in the upper half of this seed image was caused by resin from a vesicle that was ruptured in preparing the seed for photography. Seed length ~ 9 mm.


Figure 9

Figure 9
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Calocedrus decurrens seeds (surfaces not known) each with two wings, one much smaller than the other, extending beyond the micropylar end of the seeds.


Figure 10

Figure 10
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Abaxial view of a Cedrus libani seed showing integumental flaps that meet near the micropylar end. Portion of seed in view ~ 6mm.


Figure 11

Figure 11
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Abaxial view of a Larix sibirica seed. Edges of the integument (wing still attached) extend around both seed margins, the upper edge forming a small "pocket" over the micropylar end of the seed.


Figure 12

Figure 12
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Abaxial view of a Larix lyalli seed. Edges of the integument (wing still attached) extend around both seed margins, the upper edge forming a small "pocket" over the micropylar end of the seed.


Figure 13

Figure 13
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Two Pinus rigida seeds (surfaces not known) with no trace of wing or integument. Seed length ~ 4mm.


Figure 14

Figure 14
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Adaxial view of a Pinus palustris seed (left) removed from its intact integument (right). The "claw"-like nature of the integument, typical of many pine seeds, does not completely cover the adaxial or abaxial surfaces.


Figure 15

Figure 15
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Four Pseudotsuga menziesii seeds. A - intact seed, adaxial view. B - seed with wing broken off, adaxial view. C - intact seed, abaxial view, showing integument edges. D - seed with wing broken off, abaxial view. B and D would be "pure seed" according to PSD 51.


Figure 16

Figure 16
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Four Pseudotsuga macrocarpa seeds. A - intact seed, adaxial view. B - seed with wing broken off, adaxial view. C - intact seed, abaxial view. D - seed with wing broken off, abaxial view. Integument edges can be seen in C and D. B and D would be "pure seed" according to PSD 51.


Figure 17

Figure 17
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Abaxial view of a Tsuga heterophylla seed showing integument edges extending around seed margins, joining at the micropylar end to form a small "pocket". In this view the lower integument edge extends around the seed to form a flap. The oval structure near the seed centre is a large resin vesicle.


Figure 18

Figure 18
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Abaxial view of a Tsuga mertensiana seed showing integument edges extending around seed margins, joining at the micropylar end to form a small "pocket". In this view, the circular structure near the upper edge of the seed is a large resin vesicle.


Figure 19

Figure 19
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Four Keteleéria davidiana seeds. A - adaxial view of integument covering entire surface, with partial wing attached. B - abaxial view of integument flaps extending around seed margins, and partial wing. C - abaxial view of integument with flaps extending around seed margins, wing almost completely broken off. D - adaxial view integument covering entire surface (wing broken off). C and D probably would be "pure seed" according to PSD 51.

Because photographic depth of field becomes very shallow the closer the camera lens approaches the subject, all critical details, especially of the larger seeds, could not be obtained within a single frame for most specimens. Thus, several macrophotographs were made with slight focus adjustments between frames. Of the more than 250 exposures made 40-45% were scanned into the computer. Representative illustrations for species in PSD 51 only are presented here. In all figures the scale bar (when shown) indicates millimetres; arrows generally point to the edges or margins of the structures indicated, and unless otherwise indicated, all views are of abaxial surfaces. The following observations were made on the 7 genera (in alphabetical order, plus Keteleéria) currently assigned to PSD 51.

Abies
Fir seeds have been assigned, ostensibly, to PSD 51 on the basis that the integument "is rarely removed in processing, and is impossible to consistently remove, without causing damage. Hence, seed with integument attached is considered to be 'pure seed'". It was determined for all 13 fir (6 North American and 7 European/Asian/North African) species examined (Table 1) the integuments are not "fused" to the seeds as the first part of PSD 51 states. For the seeds that still retained entire wings (plus integuments), or those that retained integuments only, these structures were removed easily by hand. Moistening the seeds (placing them on moist blotter for two days, as for a germination test) made this separation straightforward. Many germination analysts will know that fir integuments - being highly hygroscopic, which causes them to expand when moist, and loosen their "grip" on the seeds - often separate from the seeds as the latter are moved around to assess germinant status.

Whereas the proximal end of the fir wing, the integument, completely covers the adaxial surface of the seed, only two "flaps" wrap around the long margins to "clasp" the seed on the abaxial surface.This is clearly shown in A. numidica (Fig. 1), and was described previously (Cermak 1987) for A. alba (Fig. 2). These abaxial flaps vary in size, one (on the margin of the seed nearer to the centre of the ovuliferous scale on which it formed) being narrow, and the other wider, sometimes almost making contact with the narrower flap, forming a "pocket" into which the seed rests.

Except for minor variations in flap size, no differences were found between North American firs, as exemplified by A. amabilis (Fig. 3) and A. procera (Fig. 4), and those from other parts of the world, as exemplified by A. nordmanniana (Fig. 5) and A. sibirica (Figs. 6-7). Fir seed coats are characterized by a number of resin vesicles that are readily ruptured (Fig. 8). Some seed workers may have found integuments fastened to the seeds because leaking resin has permeated between the seed coat and the integument/wing and, on drying, has become an adhesive. However, the integuments of fir seeds are not "fused" to the seeds in the same manner as those in other genera, notably Pseudotsuga (see below). Based on this there appears to be no reason why Abies and Pseudotsuga should be included in the same PSD.

Calocedrus (formerly Libocedrus)
PSD 51 specifically refers to "wing", rather than "wing(s)" (see PSD 49). To a casual observer, incense cedar seeds appear to bear only one wing, but actually they have two (Fig. 9). A large wing extends lengthwise beyond the seed on one side, and a second, much smaller one, barely emerges alongside the first from the opposite side. Both wings are persistent and project beyond the micropylar (rather than the cotyledon) end of the seed (Stein 1974). This genus appears to have been mis-assigned to PSD 51 for two reasons: (a) it is a member of the Cupressaceae, and (b) all Cupressaceae have two persistent wings that are difficult to remove without damaging the seeds. Therefore, Calocedrus decurrens should be included with other Cupressaceae seeds in PSD 49.

Cedrus
Cedrus libani seeds showed the same integument characteristics as fir seeds. That is, the integument covers the entire adaxial surface, but two small flaps clasp the seeds on the abaxial surface (Fig. 10). Although the seeds examined here could not be separated easily from their integuments (as were firs), it appears that Cedrus correctly belongs in PSD 51, or the PSD that includes Abies also.

Larix
The integument of larch seeds covers the entire adaxial surface (as in Abies and Cedrus). Close examination of abaxial surfaces showed what appeared to be integumental margins projecting slightly beyond the seed coat surfaces, as exemplified by L. sibirica (Fig. 11) and L. lyalli (Fig. 12), but no separable integumental layer was visible, and integuments could not be separated. In this regard, Larix seeds resembled those of Pseudotsuga (see below). Some analysts have reported difficulty in distinguishing larch wings and integuments, implying that there may be integumental separation on some occasions (perhaps due to seedlot differences?). Presently it would best to leave Larix and Pseudotsuga seeds in the same PSD, but to separate them from Abies and Cedrus.

Pinus I (P. palustris and P. rigida)
All other pine seeds (referred to as Pinus II, see above) are assigned (along with spruce) to PSD 47 in which pure seeds are completely without wing or integument, the latter not being intimately associated with the seed, and thus easily removed. Unprocessed P. rigida seeds (that is, with wings and/or integuments) were not available for comparison, but it appeared that whatever wings and integuments originally had been on the seeds examined here, they had been completely removed without apparent seed damage, and there was no trace of wing or integument on either adaxial or abaxial surfaces (Fig. 13). P. palustris seeds were easily separated from the wing/integument (Fig. 14), the integument resembling the same "claw" observed in most Pinus II species (not illustrated).

Seeds of two other pines, viz., P. aristata and P. sylvestris, together with those of P. palustris, have been described as difficult to dewing and susceptible to mechanical damage (Krugman and Jenkinson 1974). No mention was made of P. rigida seeds. Also, no mention was made of wings or integuments remaining "fused" to these seeds. Whereas it is possible that the relatively small samples of P. palustris and P. rigida seeds available may not have been representative of all seeds of these two species, it would appear that justification for their separation from other pine seeds (Pinus II species) requires confirmation.

Pseudotsuga
PSD 51 describes the integument as being "fused to the seed", and "is rarely removed in processing, and is impossible to consistently remove, without causing damage." Fused means joined as if melted together (Anon. 1987). Seeds of Pseudotsuga menziesii (Fig. 15) and P. macrocarpa (Fig. 16), fit this description. Despite large differences in physical dimensions between these two species, identical seed/wing characteristics were observed. Although margins of what appeared to be integuments were discernible projecting beyond the abaxial surfaces of many seeds, to all intents and purposes the single wing appeared to be an "outgrowth" of the adaxial surface of seed coat. That is, the integument was fused to the seed coat, which also fits the botanical description.

When seeds of this genus are processed, the wing is broken off from the seed, usually leaving a very small fringe of wing/integument tissue at the chalazal (cotyledon) end. This tissue remnant may become more abraded, and turn into dust or very small pieces, as the seeds are further handled. Although these loose impurities are easily removed, a small amount may persist after the seeds are packaged for trade. Usually Pseudotsuga seeds are among the more impurities-free conifer seeds marketed. However, because of this very trait, they are in conflict with the PSD definition that the "integument ... is impossible to consistently remove, without causing damage" for two reasons. First, in Pseudotsuga, the integument is impossible to remove at any time, and second, whereas the wings do appear to be "fused" to the seeds, they are easily and consistently removed without causing seed quality damage. It would appear, therefore, that Pseudotsuga seeds do not properly belong in PSD 51.

Tsuga
Entire wings can be removed from hemlock seeds without serious damage to seed quality (Ruth 1974). This does not specify integuments, but the word "entire" may imply this. As with fir seeds, hemlock integuments appear to clasp the seeds. The integument covers the entire adaxial surface, but wraps around the seed on the abaxial surface as two small flaps, shown here for T. heterophylla (Fig. 17) and T. mertensiana (Fig. 18). One flap (on the margin of the seed nearer to the centre of the ovuliferous scale on which it formed) is very narrow, usually not extending beyond the seed margin. The second flap, extending around the other margin of the seed, is wider and while it wraps around further at the micropylar end, it is quite short so that only the tip of the seed is "enclosed".

Hemlock integuments are highly hygroscopic and expand when wet. Attached integumental remnants often come loose during the germination test (as in fir) as seeds are moved around for germinant assessment. Also similar to fir, hemlock seed coats bear resin vesicles, some being large and prominent relative to seed size (Fig. 17). Although not as easily ruptured as those in fir seed coats, if broken the leaked resin may firmly adhere the remaining integument to the seed coat, thus giving the appearance of the two being "fused". Based on these observations, Tsuga (like Abiesand Cedrus) seeds should not be in the same PSD as Pseudotsuga.

Keteleéria
Keteleeria, together with fir and cedar [and Pseudolarix, golden larch (Dallimore and Jackson 1954)], are the only members of the Pinaceae with upright cones. Although Keteleéria cones do not disintegrate at maturity (which distinguishes them from Abies, Cedrus and Pseudolarix), this genus is considered to be most-closely related to Abies (Rehder 1958). Keteleeria seeds resemble those of fir, perhaps more so than those of cedar (Fig. 19). The integument covers the entire adaxial surface, terminating on the abaxial surface as two flaps. Like the cedar seeds examined, it was not possible to separate integuments from these Keteleéria seeds, which were old (>30 years) and quite fragile. Based on these observations, should Keteleeria be included in ISTA prescriptions at some future date, they should be placed alongside fir and cedar in the same PSD.

Sequoiadendron
Sequoiadendron seeds currently are assigned to PSD 50 together with Acacia, Cytisus, and Mahonia. While seeds of the latter-named genera were not examined, it appears that Sequoiadendron is misplaced because giant redwood seeds do not form arils - neither does Acacia (Whitesell 1974) or Cytisus (Gill and Pogge 1974); Mahonia forms berries (?). Sequoiadendron should be included with other Cupressaceae seeds in PSD 49, along with Sequoia.

Taxus
Yew is currently assigned to PSD 10, which covers more than 160 genera ranging from Abelmoschus (Malvaceae) to Vinca (Apocynaceae) (ISTA 1999, pp: 123-132), and includes three coniferous genera, viz., Juniperus (Cupressaceae), Taxodium (Taxodiaceae), and Taxus (Taxaceae). However, PSD 10 makes no mention of "aril", the fleshy, brightly-coloured, cup-like, fruit that bears the single yew seed, and which is a major recognition feature for the genus. Yet PSD 50, which includes, Cytisus, Mahonia and, currently, Sequoiadendron (quod vide), speaks of the presence/absence of the "aril". It would appear that the single-seeded arils of Taxus fruits and the several-seeded indehiscent strobili commonly called "berries" of Juniperus (Johnsen and Alexander 1974) have been mistakenly compared and, hence, have both been assigned to PSD 10. From work experience with T. brevifolia and J. scopulorum, it is suggested that these two genera do not belong in the same PSD and that, more likely, Taxus seeds would be better re-assigned to PSD 50. The assignment to PSD 10 of Juniperus seeds needs to be confirmed, as is the inclusion of Taxodium distichum, which produces two-seeded cones (Bonner 1974).

Conclusions

Several anomalies were reported and questions raised concerning the assignments of conifer genera to ISTA Pure Seed Definitions (PSDs). In alphabetical order by genus these were:

  1. Abies (also Cedrus and Tsuga; plus Keteleéria), with their integuments "intimately associated" with, but not "fused" to, the seeds, should not be in the same PSD as Pseudotsuga (and possibly Larix). PSD 51 needs revision.
  2. Calocedrus decurrens bears two non-removable wings, as do other members of the Cupressaceae, and should be re-assigned to PSD 49.
  3. Cedrus - see Abies (and Tsuga).
  4. Keteleéria (not presently covered by ISTA prescriptions), should be included with Abies, Cedrus and Tsuga.
  5. Larix seeds appear to have integuments "fused" to the seeds, similar to Pseudotsuga. However, because the wings are easily removed in operational dewinging, without damaging the seeds, PSD 51 does not entirely apply. A new definition is recommended. (See also Pseudotsuga.)
  6. Pinus palustris and P. rigida seeds, assigned to PSD 51, appeared to be no different from other Pinus II pines assigned to PSD 47. Unless there is contrary evidence, these two pine species should be re-assigned to PSD 47.
  7. Pseudotsuga seeds appear to have integuments "fused" to the seeds, similar to Larix. However, because the wings are easily removed in operational dewinging, without damaging the seeds, PSD 51 does not entirely apply. A new definition is recommended. (See also Larix.)
  8. Sequoiadendron gigantea does not form arils. Seeds of this species bear two non-removable wings, similar to other members of the Cupressaceae, and should be re-assigned to PSD 49.
  9. Taxus seeds are formed in fleshy arils, which are not to be compared with juniper "berries". Taxus should be re-assigned to PSD 50, and the assignment of Juniperus and Taxodium to PSD 10 needs to be confirmed.
  10. Tsuga (also Abies and Cedrus; plus Keteleeria), with their integuments "intimately associated" with, but not "fused" to, the seeds, should not be in the same PSD as Pseudotsuga (and possibly Larix). PSD 51 needs revision.

The observations on which these conclusions have been made are based solely on surface features of seeds of the genera concerned. No study of tissue development was possible. However, the major details discussed, especially the "fused" integuments of Pseudotsuga and (possibly) Larix, as well as how the integuments of other genera form, require microscopic examination of developing seeds, that is, prior to and through seed maturation. This is the type of work ideally suited to graduate student research, and should be encouraged.

Literature cited

Anon., 1987. The New Lexicon Webster's Dictionary of the English Language. Lexicon Publications, Inc., New York, pp.1149 (+ supplements).

AOSA [Association of Official Seed Analysts], 1998. Rules for testing seeds (revised 2001). Lincoln, NE: Association of Official Seed Analysts, 126 pp.

Bonner, F.T., 1974. Taxodium distichum (L.) Rich. Baldcypress. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 796-798.

Bonner, F.T., 1984. Glossary of seed germination terms for tree seed workers. General Technical Report S0-49, New Orleans, Louisiana, U.S. Forest Service, Southern Forest Experiment Station, pp. 4.

Cermak, J. 1987. Monoterpene hydrocarbon contents of the resin from seeds of silver fir (Abies alba Mill.). Trees: Structure and Function vol. 1: 94-101.

Copeland, L.O., 1976. Principles of seed science and technology. Burgess Publishing Co., Minneapolis, Minnesota, 369 pp.

Dallimore, W. and A.B. Jackson, 1954. A handbook of the coniferae including Ginkgoaceae. Edward Arnold Publishers, London, 686 pp.

Felfoldi, E.M., 1987. Handbook of Pure Seed Definitions with illustrations (excluding forest tree seeds) (2nd. ed.). International Seed Testing Association, P.O. Box 308, Zuerichstrasse 50, 8303 Bassersdorf, CH-Switzerland, pp.59.

Gill. J.D. and Pogge, F.L., 1974. Cytisus scoparius (L.) Lk. Scotch broom. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 370-371.

ISTA [International Seed Testing Association], 1999. International Rules for Seed Testing. Seed Science & Technology, vol. 27, Supplement, pp.333 (+ Guidelines I-VII).

Johnsen, T.N. and Alexander, R.A., 1974. Juniperus L. Juniper. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 460-469.

Krugman, S.L. and Jenkinson, J.L. 1974. Pinus L. Pine. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 598-638.

Rehder, A., 1958. Manual of cultivated trees and shrubs hardy in North America exclusive of the subtropical and warmer temperate regions. Second edition, revised and enlarged, New York, Macmillan, pp. 920.

Ruth, R.H., 1974. Tsuga (Endl.) Carr. Hemlock. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 819-827.

Stein, W.I., 1974. Libocedrus decurrens Torr. Incense-cedar. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 494-499.

Whitesell, C.D., 1974. Acacia Mill. Acacia. In, Schopmeyer, C.S. (tech. coord.), Seeds of Woody Plants in the United States. Agriculture Handbook 450, Forest Service, U.S. Dept. of Agriculture, Wash., D.C., pp. 184-186.

Table 1. Genera and species examined in relation to ISTA (1999) Pure Seed Definitions.

Genus Species
Abies alba*, amabilis*, balsamea*, concolor*, fabri*, grandis*, lasiocarpa*, magnifica*, nordmanniana*, numidica*, pinsapo*, procera*, sibirica*
Calocedrus decurrens*
Cedrus libani*
Chamaecyparis nootkatensis
Cupressus funebria
Keteleéria davidiana*
Larix decidua*, leptolepis*, lyalli*, occidentalis*, sibirica*
Picea alba, glauca, pungens, purpurea
Pinus contorta, coulteri, palustris, ponderosa, rigida
Pseudotsuga macrocarpus*, menziesii*
Sequoiadendron gigantea
Thuja plicata, occidentalis
Tsuga heterophylla*, mertensiana*

* Species covered by this report (but not all illustrated).

Citation

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.