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Section A. Structure and Specialized Characters:
[A. Seed Parts] [B. Seed Types] [C. Embryo Parts] [D. Embryo Types] [E. Aril Structural Types and Selected Seed Surface Features] [F. Seedling Parts] [G. Seedling Types]
XII. Seeds and Seedlings
- Aril. Outgrowth of funiculus, raphe, or integuments; or fleshy integuments or seed coat, a sarcotesta.
- Chalaza. Funicular end of seed body.
- Embryo. Young sporophyte consisting of epicotyl, hypocotyl, radicle, and one or more cotyledons.
- Endosperm. Food reserve tissue in seed derived from fertilized polar nuclei; or food reserve derived from megametophyte in gymnosperms.
- Hilum. Funicular scar on seed coat.
- Micropyle. Hole through seed coat.
- Perisperm. Food reserve in seed derived from diploid nucellus or integuments.
- Raphe. Ridge on seed coat formed from adnate funiculus.
- Seed Coat. Outer protective covering of seed.
B. Seed Types
(Classification based on type of nourishing tissue)
- Cotylespermous. With food reserve in cotyledon, derived from zygote.
- Endospermous or Albuminous. With food reserve in endosperm or albumen, derived from fertilized polar nuclei.
- Hypocotylespermous or Macropodial. With food reserve stored in hypocotyl, derived from zygote.
- Perispermous. With food reserve in perisperm, derived from diploid nucellus or integuments.
- Coleoptile. Protective sheath around epicotyl in grasses.
- Coleorhiza. Protective sheath around radicle in grasses.
- Cotyledon. Embryonic leaf or leaves in seed.
- Epicotyl. Apical end of embryo axis that gives rise to shoot system.
- Hypocotyl. Embryonic stem in seed, located below cotyledons.
- Plumule. Embryonic leaves in seed derived from epicotyl.
- Radicle. Basal end of embryo axis that gives rise to root system.
- Bent. Foliate embryo with expanded and usually thick cotyledons in an axile position bent upon the hypocotyl in a jacknife position.
- Broad. Basal, globular or lenticular embryo in copious endosperm.
- Capitate. More or less basal head-like or turbinate embryo in copious endosperm.
- Dwarf. Axial embryo variable in size relative to seed, small to nearly total size of seed; seeds 0.2 - 2 mm. long.
- Folded. Foliate embryo with cotyledons usually thin and extensively expanded and folded in various ways.
- Investing. Axial embryo usually erect with thick cotyledons overlapping and encasing the somewhat dwarfed hypocotyl; endosperm wanting or limited.
- Lateral. Basal or baso-lateral embryo, discoid or lenticular, usually surrounded by copious endosperm.
- Linear. Axial embryo several times longer than broad, straight, curved or coiled; cotyledons not expanded; endosperm present or absent.
- Micro. Axial embryo in minute seeds, less than 0.2 mm. long; minute and undifferentiated to almost total size of seed.
- Peripheral. Peripheral embryo large and elongate, arcuate, annular, spirolobal, or straight; cotyledons narrow or expanded; perisperm central or lateral.
- Rudimentary. Basal, small nonperipheral embryo in small to large seed; relatively undifferentiated; endosperm copious.
- Spatulate. Foliate, erect embryo with variable cotyledons, thin to thick and slightly expanded to broad.
1. Aril Structural Types
- Arillate. General term for an outgrowth from the funiculus, seed coat or chalaza; or a fleshy seed coat.
- Carunculate. With an excrescent outgrowth from integuments near the hilum, as in Euphorbia.Fibrous. With stringy or cord-like seed coat, as mace in Myristica.
- Funicular. With a persistent elongate funiculus attached to seed coat, as in Magnolia.
- Sarcous. With the seed coat fleshy.
- Strophiolate. With elongate aril or strophiole in the hilum region.
2. Special Seed Surface Features
(See Surface in Section B of this chapter)
- Alate. Winged.
- Circumalate. Winged circumferentially.
- Comose. With a tuft of trichomes.
- Coronate. With a crown.
- Crested. With elevated ridge or ridges, raphal.
- Umbonate. With a distinct projection usually from the side.
- Verrucose. Warty.
- Cataphyll. Rudimentary scale leaf produced by seedling, usually in cryptocotylar species.
- Collet. External demarcation between hypocotyl and root.
- Eophyll. Term applied to first few leaves with green, expanded lamina developed by seedlings; transitional type leaves developed before formation of adult leaves.
- Metaphyll. Adult leaf.
G. Seedling Types
(Classification based on position of cotyledons in germination)
- Cryptocotylar or Hypogeous. With the cotyledons remaining inside the seed; seed usually remaining below ground
- Phanerocotylar or Epigeous. With the cotyledons emergent from seed, usually appearing above ground.
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