120 



COLLEGE BOTANY 



and that most of the reserve food is stored around the embryo 

 instead of in the cotyledons. The seeds of the beet, tomato, 

 pepper, buckwheat and many of our common weeds belong to this 

 type, but owing to their small size are not so satisfactory 

 for study. 



Germination of the Castor-Oil Seed. This process is very 

 similar to that of the bean, but the cotyledons are covered for 



FIG. 85. Seed of castor-oil plant; (a) and (6) upper and lower surfaces; (c) after removal of the 

 seed coat; (d, e) cotyledon showing leaf characters. 



some time by the endosperm, which they gradually absorb. As 

 the endosperm disappears, the cotyledons become green and more 

 leaf-like and frequently persist for a long time. 



Therefore, the cotyledons serve first for the absorption of 

 stored food and later as foliage, 



The Corn Type. This is a monocotyledonous type in which 

 the food is stored in the endosperm. It is not a simple seed, but 

 a true caryopsis fruit (page 112) in which the ovary coats have 

 united with the seed coats. Therefore, it is not strictly com- 

 parable to the seeds of the bean and castor-oil bean. It is 

 flattened and somewhat wedge-shaped, the edges rounded and the 

 large end smooth or indented. On one side is a groove within 

 which the embryo is clearly visible. If we cut the grain longi- 

 tudinally, we find the parts as follows: the radicle or primary 



