Section A. Structure and Specialized Characters:
XII. Seeds and Seedlings

[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]

A. Seed Parts (Figure 6-10-3)

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.

C. Embryo Parts (Figure 6-10-3)

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.

D. Embryo Types (Figure 6-10-4)
(Classification based primarily on embryo shape, size, and position-adapted from Martin [1946])

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.

E. Aril Structural Types and Selected Seed Surface Features

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.

F. Seedling Parts
(Specialized parts only--adapted from Duke [1969])

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.