GERMINATION OF BEAN 



167 



Fig. 284. Try this 



be- 



288. Germination of eas 

 tor bean. Endospern 



and they assume grotesque forms, 

 with peas and beans. 



312. The first internode above the cotyledons 

 tweeu the cotyledons and the plumule — is 

 the epicotyl. It elevates the plumule into the 

 air, and tlie pi immle- leaves expand into the ^^j 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 

 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 



cotyledons or "halves of the beau," 



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

 They often become green and probably 

 perform some function of foliage. Be- 

 (tause of its large size, Lima bean shows 

 all these parts well. 



314. GERMINATION OF CASTOR BEAN. 

 — In the castor beau the hilum and 

 niicropyle are at the smaller end (Fig. 



290. Germination complete 

 in castor bean 



istor l,ean. Endo- 

 sperm at o, o ; cotyle- 

 <li>n» at b. 



