Questa introduzione alla botanica riguarda i processi di germinazione dei semi, compresa la germinazione epigeale e ipogea. Esempi includono piselli e fagioli di canale per epigeo e fagioli di canale scarlatti per germinazione ipogea.
1855 x 1347 px | 31,4 x 22,8 cm | 12,4 x 9 inches | 150dpi
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. Beginners' botany. Botany. SEEDS AND GERMINATION 23. Fig. 17. — Pea. Grotesque forms assumed when the roots cannot gain entrance to the soil. air, germination is said to be epigeal (" above the earth "). Bean and pumpkin are examples. When the hypocotyl does not elongate greatly and the cotyledons remain under ground, the germi- nation is hypogeal ("be- neath the earth"). Pea and scarlet runner bean are examples (Fig. 48). When the germinating seed lies on a hard sur- face, as on closely com- pacted soil, the hypocotyl and rootlets may not be able to secure a foothold and they assume grotesque forms. (Fig. 17.) Try this with peas and beans. The first internode ("between nodes") above the coty- ledons is the epicotyl. It elevates the plumule into the air, and the plumule-leaves expand into the first true leaves of the plant. These first true leaves, however, may be very unlike the later leaves in shape. Germination of Bean. — The common bean, as we have seen (Fig. 15), has cotyledons that occupy all the space inside the seed-coats. When the hy- pocotyl, or elongated caulicle, emerges, the plumule-leaves have begun to en- large, and to unfold (Fig. 18). The hypocotyl elongates rapidly. One end of it is held by the roots.' The othei is held by the seed-coats in the soil. It therefore takes the form of a loop, and the central part of the loop " comes up " first {a, Fig. 19). Presently the cotyledons come out of the seed-coats. Fig. iS. — Cotyledons OF Germinating Bean spread apart TO SHOW Elongat- ing Caulicle and Plumule.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Bailey, L. H. (Liberty Hyde), 1858-1954. New York, The Macmillan company
