42 



HORTICULTURE FOR SCHOOLS 





52. The pumpkin seed. In the pumpkin seed, the testa 

 (outer coat) is thick and hard, and when it is removed a thin 



inner green coat may be seen. The 

 cotyledons are thin, flat, and large. 

 When the seed has been soaked, 

 veins in the cotyledons show dis- 

 tinctly. The thin cotyledons of 

 the pumpkin seed contain a much 

 smaller amount of stored food than 

 is present in those of the pea or 

 bean; therefore, the young pump- 

 kin plant must manufacture plant- 

 food early. It does this by bringing 

 the cotyledons up into the air as 

 soon as possible, where they turn 



FIG. 22. Germination of pumpkin green and function as leaves while 



the true leaves are forming. As 

 the cotyledons of the pumpkin 



remain on the plant permanently and act as leaves, they are 



part of the embryo. 



The pumpkin seed has quite a struggle to free itself from 



the tough testa. After the seed-coat cracks and the caulide 



projects, a protuberance called the peg 



is developed at just the right place on 



the caulicle to catch hold of the split 



testa in such a manner as to pull it off 



the seed as the cotyledons are drawn 



upward (Fig. 22). 



53. The corn. Another type of seed 

 is represented by the corn. The two 

 sides of the kernel are illustrated in 

 Fig. 23. One side is flat and smooth, 

 while the other has a slight depressioa, 



lighter in color than the surrounding portions. Under 

 this lies the embryo and the cotyledon. If a soaked 



FIG. 23. Exterior of the flat 

 surfaces of a kernel of corn. 

 A shows the slight depres- 

 sion under which lies the 

 embryo; B, the opposite 

 flat side. 



