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? 
Fia. 59.— Stages in the germination of a typical seedling of the squash family : 
u, a seed before germination ; }, 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; pl, 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 
