218 SCHOOL AND HOME GARDENS 
cotyledons, which contain veins. When the castor bean 
germinates, the hypocotyl forms a loop that pulls up 
the cotyledons inclosed by the endosperm. The hard 
testa gradually slips off, and the endosperm is absorbed 
until nothing but a thin film remains. The cotyledons 
grow to form green 
leaves, which serve 
the plant as foliage 
for some time. 
Plant several rows of 
castor beans in a box. After 
the fifth day, take up one 
row every third day and 
study the development of 
the parts. Leave some of the 
plants in the box until the 
cotyledons drop off. 
Note that the plumule 
Fig. 121. The Castor-Bean Plant does not develop so rapidly 
At the left the cotyledons are held In the castor bean as in the 
ae bean and that the cotyledons 
grow until they become of considerable size, while those 
of the bean soon shrivel up and drop off. 
Germination of a grain of corn. When a grain of comm 
germinates, the primary root, or the radicle. grows 
toward the narrow end of the grain and breaks out of 
its sheath near the hilum; the plumule makes its appear- 
ance at the opposite end. The young plant obtains 
some food from the cotyledon, but the greater part of 
