. Botany for agricultural students . Botany. 56 SEEDS AND FRUITS young plant, which after reaching a certain stage of development, varying in different plants, passes into a dormant stage from which it may awake if conditions are favorable and continue its devel- opment until it becomes a mature plant. In the development of the embryo from the fertilization of the egg to the dormant stage, certain structures which function in the further development of the young plant are usually more or less developed. In a well formed embryo like that of the Bean, there are four parts, hyocotyl, plumule, cot
. Botany for agricultural students . Botany. 56 SEEDS AND FRUITS young plant, which after reaching a certain stage of development, varying in different plants, passes into a dormant stage from which it may awake if conditions are favorable and continue its devel- opment until it becomes a mature plant. In the development of the embryo from the fertilization of the egg to the dormant stage, certain structures which function in the further development of the young plant are usually more or less developed. In a well formed embryo like that of the Bean, there are four parts, hyocotyl, plumule, cotyledons, and radicle. In Figure 60 of the Bean, h is hypocotyl, p, plumule, and c, cotyledons. The radicle (r) is at the lower end of the hypocotyl and is so closely joined with the hypocotyl that it does not appear as a separate structure. The cotyledons of the Bean have absorbed the endo- sperm and consequently are so much enlarged that the}^ form the bulk of the embryo. The special functions performed by the different parts of the embryo are quite noticeable in the germination of the seed. The cotyle- dons supply food; the plumule develops Fig. 60. Bean with testa gtem and leaves; the radicle develops removed and cotyledons , i i, i. i • J ^ :' , , a root; and the hypocotyl in many spread apart, c, cotyledons; , , h, hypocotyl; p, plumule; r, ^ases pulls the cotyledons and plumule radicle. out of the seed coat and raises them above ground. The stored food and seed coat are temporary structures. They nourish and protect the young plant in its early stage of develop- ment and then disappear. The stored food, consisting chiefly of starch, proteins, and oils, the proportion varying in different seeds, develops in close contact with the embryo and when not absorbed as rapidly as it develops, it forms the storage tissue or endosperm in which the embryo becomes imbedded. The testa, the protective structure of the seed and usually formed from the integuments of the ovule, gene
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
