GERMINATION IN PARTICULAR SEEDS 



175 



317. Sprout- 

 ing Indian 

 corn. Hi- 

 lum at h; 



micropyle 

 at d. 



318. Kernel of 

 Indian corn. 

 Caulicle at 

 6; cotyledon 

 a ; plumule 

 P- 



its central part "comes up" first, (a, Fig. 312.) Presently 



it draws the cotyledons out of the seed-coats, and then it 



straightens and the cotyledons expand. These coty- 



fflT/j ledons, or "halves of the bean," persist for some 



Br! time. (6, Fig. 312.) They often become green and 



probably perform some function of 



foliage. Because of its large size, Lima 



bean shows all these parts well. 



342. Germination of Castor Bean. 

 — In the castor bean the hilum and 

 micropyle are at the smaller end. (Fig. 

 313.) The bean "comes up" with a 

 loop, which indicates that the hypocotyl 

 greatly elongates. On exam- 

 ining a germinating seed, however, it will be 

 found that the cotyledons are contained inside 

 fleshy body or sac. (a, Fig. 314.) This 

 sac is the endosperm. To its inner sur- 

 face the thin, veiny cotyledons are 

 very closely appressed, absorbing its 

 substance. (Fig. 315.) The cotyledons 

 increase in size as they reach the air (Fig. 316), and become 



functional leaves. 



J 343. Germination of Indian Corn. — Soak kernels of 



I corn. Note that the micropyle and hilum are at the 



(I ~ smaller end. (Fig. 317.) Make a longi- 



A [ tudinal section through the narrow 



^^^Jp^^:^ diameter; Fig. 318 shows it, The 



Pi l^ptf? w single cotyledon is at a, 



the caulicle at b, the 



plumule at p. The 



cotyledon remains in 



the seed. The food is 



stored both in the cotyledon and as endosperm, chiefly the 



latter. The emerging shoo,t is the plumule, with a sheathing 



319. Indian corn. Cau- 

 licle at c; roots emerg- 

 ing at m; plumule at p. 



Indian corn. o. plumule; 

 n to p, epicotyl. 



