. Botany for agricultural students . Botany. NATURE AND STRUCTURE OF SEEDS 57 On the surface of seeds occur certain structures which suggest the structural relation of the seed to the ovule. The micropyle, the small opening through which the pollen tube entered the ovule, persists as a tiny pit on the seed coat. Usually near the micropyle there is a much larger scar, called the hilum, left where the seed broke away from the funiculus, the stalk-like structure which attached the ovule to the ovary and through which the seed received food and water during its development. {Fig. 61.) In case an o
. Botany for agricultural students . Botany. NATURE AND STRUCTURE OF SEEDS 57 On the surface of seeds occur certain structures which suggest the structural relation of the seed to the ovule. The micropyle, the small opening through which the pollen tube entered the ovule, persists as a tiny pit on the seed coat. Usually near the micropyle there is a much larger scar, called the hilum, left where the seed broke away from the funiculus, the stalk-like structure which attached the ovule to the ovary and through which the seed received food and water during its development. {Fig. 61.) In case an ovule turns over on its elongated stalk and grows fast to it, the stalk persists on the seed coat as a distinct ridge, called the ra-phe. {Fig. 62.) In some seeds, like those of r--\ A B ^ Fig. 62. — A, seed of Pansy showing raphe {r). B, seed of Castor Bean show- ing caruncle (c). C, seed of White Water Lily showing the aril or loose jacket around the Fig. 61. — Beans showing the hylum at h and the micropyle at m. the Castor Bean, an enlargement known as the caruncle develops near the micropyle. Structures such as hairs, plumes, hooks, and other appendages which do not occur on ovules, are direct outgrowths of the seed coat and function chiefly in dissemination. Similar appendages occur often on one-seeded ovaries in which case one can tell only by dissection whether the structure is a seed or one-seeded fruit. Many of the small one-seeded fruits are commonly called seeds. In addition to a seed, they contain the ovary wall which persists as an outer covering over the seed. The so-called seeds of Let- tuce, Buckwheat, Ragweed, and the grains such as Corn, Wheat, Barley, Rye, and Oats are familiar examples of one-seeded fruits which are commonly called seeds. While they are not identical with true seeds in structure, they are in function and therefore may be appropriately discussed with seeds. In these one-seeded fruits, the seed is protected by the hardened ovary wall
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
