SEED GERMINATION 



63 



family, and hence all of our cereal crops, as com, wheat, 

 rice, oats, barley and rye, for they are all grasses. 



The dicotyledons include the clovers, beans, peas, 

 cotton, the common vegetables, and broad-leaved plants 

 generally. 



When we ex- 

 amine the seed of 

 either of these two 

 classes of plants, 

 we are usually 

 easily able to 

 distinguish the 

 parts. We find 

 the embryo, or 

 germ, in the mono- 

 cotyledons at the 

 base of the seed, 

 as in the case of 

 corn, and having 

 but one cotyledon, 

 while the stored 

 food occupies a 

 large space outside 

 the embryo and 

 is called the endo- 

 sperm. In the 

 seeds of the di- 

 cotyledons, there 

 is no endosperm, or food, stored on the outside of the 

 embryo. The food is contained in the cotyledons in- 

 stead, which accounts for their large size. They occupy 

 the entire space within the seedcoat, or hull, except 

 that taken up by the little plumule and hypocotyl. 

 Study carefully Figure 18, noting particularly the plumule 



Fig. 18. — Corn and bean showing parts ; the 

 embryo of each removed. 



, cotyledons ; b, plumules ; c, hypocotyl, the 

 lower end of which is called the radicle ; d, 

 endosperm. 



