44 



PRACTICAL COURSE IN BOTANY 



WTiat changes have the cotyledons undergone in the suc- 

 cessive seedUngs? Remove from the earth a seedling just 

 l)eginuing to sprout and sketch it. From what point does 

 the h ypocotyl protrude through the coats ? Does this agree 

 with its position as sketched in your study of the seed? 

 In which part of the embryo does the first growth take place? 



Remove in succession the several seedlings you have 

 sketched and note their changes. How does the root differ 

 from that of the corn and oats ? The first root formed by the 

 extension of the hypocotyl is the primary root and should be 

 so labeled in your drawings ; the branches that spring from 

 it are secondary roots. Look for root hairs; if there are 

 any, where do they occur? 



43. Germination of the squash. — How^ does the manner 

 of breaking through the soil compare with that of the bean ? 



Co 





e c b a 



Fig. 59. — Stages in the germination of a typical seedling of the squash family : 

 z, a seed before germination ; b, c, e, the same in different stages of growth ; d, the 

 empty testa, with kernel removed ; hi, hilum ; m, micropjde ; p, p, the peg in the heel ; 

 h, h, h, the hypocotyl ; (ir, arch of the hypocotyl ; co, cotyledons ; pi, plumule ; ^jr, 

 primary root ; sc, secondary roots. 



With the corn? From which end of the seed, the large or 

 the small one, does the hypocotyl spring ? Do the cotyledons 

 come above ground ? How do they get out of the seed coat ? 

 Notice the thick protuberance developed by the hypocotyl 

 and pressing against the lower half of the coat at the point 

 where the hypocotyl breaks through. This is called the 



