GEKMINATION OF BEAN 



167 



288. Germination of cas- 



and they assume grotesque forms. Fig. 284. Try this 

 with peas and beans. 



312. The first internode above the cotyledons be- 

 tween the cotyledons and the plumule is 

 the epicotyl. It elevates the plumule into the 

 air, and the plumule- leaves expand into the 287 Sprouting of 

 first true leaves of the castor bean. 

 plant. These first true leaves, however, 

 may be very unlike the later leaves. 



313. GERMINATION OF BEAN. The 

 common bean, as we have seen (Fig. 

 282) has cotyledons which occupy all 

 the space inside the seed -coats. When 

 the hypocotyl or elongating caulicle 

 emerges, the plumule -leaves have begun 



tor bean. Endosperm to enlarge and to 



unfold (Fig. 285). 



The hypocotyl elongates rapidly. One 



end of it is held by the roots. The 



other is held by the seed -coats in the 



soil. It, therefore, takes the form of 



a loop, and its central part "comes 



up" first (a, Fig. 286). Presently 



it draws the cotyledons out of the 



seed -coats, and then it straightens 



and the cotyledons expand. These 2 9o. Germination complete 



cotyledons or "halves of the bean," 



persist for some time, (&, Fig. 286). 

 They often become green and probably 

 perform some function of foliage. Be- 

 cause of its large size, Lima bean shows 

 all these parts well. 



314. GERMINATION OF CASTOR BEAN. 

 289 castor bean Endo- In the castor bean the hilum and 



S m at1. a ' a;c tyle " micropyle are at the smaller end (Fig. 



