COTYLEDON (Gr. a cup or cup-shaped hollow), or SEED-LOBE, in botany, a principal part of the embryo in phanerogamous or flowering-plants. Cryptogamous plants are acolytedonous (q.v.); their seeds or spores have no. cotyledons. Phanerogamous plants are divided according to their seeds into monocotyledonous (q.v.), having only one C., and dicolykdonoos (q.v.), having two cotyledons. With the latter are nulled some conifer remarkable for having more than two cotyledons, which form a sort of whorl. The coty ledons inclose the plumule or gemmule; and in germination they usually come above ground as the first leaves (seed-leaves) of the young plant—the plumule in dicotyledo nous plants, appearing between them—and they become at the same time more leaf-like; but in some plants, which have thick fleshy cotyledons, they remain under-ground. In either ease, they contain a store of nourishment, by which young plant is sustained on its first germination. Instances of cotyledons remaining under-ground, may be seen in the common pea and bean; and instances of cotyledons coming above-ground, in the kidney-bean and scarlet-runner, plants of the same natural order. Cotyledons are some
times very thick, sometimes very thin and delicate; those of the same seed are gener ally clual, but not always so; they are frequently undivided, but sometimes cut lobed. The cotyledons of dicotyledonous plants are often simply applied face to face; when if the radicle is folded along their edges, they are said to oe accumbent; if it is folded on their back. they are incumbent. Sometimes the two cotyledons of a seed arc condupticate, or laterally folded; sometimes they are reclinate. or folded from apex to base; somethnescoarobtte, or laterally rolled up; sometimes circinate, or spirally rolled up with the apex innermost. These terms are of importance in descriptive botany, as characters of high value are often furnished by the seed.