44 



PRACTICAL COURSE IN BOTANY 



What changes have the cotyledons undergone in the suc- 

 cessive seedlings? Remove from the earth a seedling just 

 beginning to sprout and sketch it. From what point does 

 the hypocotyl 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 ? 



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

 a, a seed before germination ; 6, c, e, the same in different stages of growth ; d, the 

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

 h, h, h, the hypocotyl ; ar, arch of the hypocotyl ; co, cotyledons ; pi, plumule ; pr, 

 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 



