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cotyledon |
Also found in: Dictionary/thesaurus, Medical, Wikipedia, Hutchinson | 0.02 sec. |
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cotyledon (kŏt'əlēd`ən), in botany, a leaf of the embryo of a seed seed, fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material, and a protective outer seed coat. Seeds are frequently confused with the fruit enclosing them in flowering plants as in the grains and nuts. ..... Click the link for more information. . The embryos of flowering plants, or angiosperms angiosperm (ăn`jēəspûrm') ..... Click the link for more information. , usually have either one cotyledon (the monocots) or two (the dicots). Seeds of gymnosperms, such as pines, may have numerous cotyledons. In some seeds the cotyledons are flat and leaflike; in others, such as the bean, the cotyledons store the seed's food reserve for germination and are fleshy. In most plants the cotyledons emerge above the soil with the seedling as it grows. They differ in form from the true leaves. cotyledonSeed leaf within the embryo of a seed that provides energy and nutrients for the developing seedling. After the first true leaves have formed, they wither and fall off. Flowering plants whose embryos have a single cotyledon are grouped as monocots, or monocotyledonous plants; embryos with two cotyledons are grouped as dicots, or dicotyledonous plants. Unlike flowering plants, gymnosperms usually have several cotyledons rather than one or two. cotyledon 1. Botany a simple embryonic leaf in seed-bearing plants, which, in some species, forms the first green leaf after germination 2. Anatomy a tuft of villi on the mammalian placenta cotyledon [‚käd·əl′ēd·ən] (botany) The first leaf of the embryo of seed plants. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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| These historians resemble a botanist who, having noticed that some plants grow from seeds producing two cotyledons, should insist that all that grows does so by sprouting into two leaves, and that the palm, the mushroom, and even the oak, which blossom into full growth and no longer resemble two leaves, are deviations from the theory. It can be shown that plants most widely different in habit and general appearance, and having strongly marked differences in every part of the flower, even in the pollen, in the fruit, and in the cotyledons, can be crossed. |
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