66 THE PLANT: A GENERAL EXTERNAL VIEW 



itself. In this kind of seed the embryo has grown to fill 

 the whole of the inside. But these fat halves, filled with 

 food, are not that part of the embryo which develops 



into the new plant. These fat 

 halves are cotyledons, and at 

 the end of one of them, on its 

 inner face, you will find a tiny 

 structure, slightly bent. This 

 tiny structure is the part of 

 the embryo which will develop 

 into the new plant. As it 

 grows, it will draw into itself 

 the food which is in the cotyle- 

 dons, and they will gradually 

 wither and die. (See Figure 22.) 

 But not all seeds are formed 

 on the same plan as the bean 

 or the peanut. As you find 

 variety in flower forms, so you 

 find variety in seed forms. 

 Thus in corn you find that 

 the embryo does not fill the 

 whole inside of the seed. It 

 occupies only a small part at 

 one end. The rest is filled with food, but the food part of 

 this kind of seed is called endosperm, not cotyledons. The 

 embryo in seeds like corn has but one cotyledon instead 

 of two, and it is but a small structure, not enlarged and 

 swollen with the food supply. (See Figure 23.) 



But, whatever the structure, the end to be secured by 

 the seed is always the same. Seeds always contain a 

 supply of food stored for the use of the little plant when 



T\ 



FIG. 22. Two views of a bean, and 

 two young stages of the plant 

 which grows from it. 



