6o 



THE LIFE OF THE PLANT 



growing parts. Yet, notwithstanding its rapid growth, 

 it is just at this period of germination that the plant is 

 practically independent of the soil. As a rule germina- 

 tion takes place in the soil ; but here is a brush-like mass 

 of green cress grown on felt, and there are seeds of 

 maize and beans grown on thin gauze net and, therefore, 

 surrounded merely by air and having their root-tips only 

 in distilled water. 



On examining germinating seeds such as beans more 

 closely, we notice that while the root and the stem 



with its young leaves in- 

 crease in size, the first pair 

 of leaves, the cotyledons, be- 

 come wrinkled, are gradually 

 absorbed, and become smaller 

 (fig. 20). This observation 

 may serve as an indication 

 of the fact that the develop- 

 ment of some parts of a shoot 

 takes place at the expense of 

 others. 



Other seeds, such as grasses, 

 present a somewhat more com- 

 plicated structure than the 

 seeds of beans. If we split a 

 grain of wheat longitudinally, 

 we find under the seed-coat 

 two perfectly distinct parts 

 (see fig. 21: b, whole grain ; c, d, 

 the separate parts). At the 

 base of the figure, a little to 

 one side, there is a small body 

 which is simply a seedling, an embryonic plant, such as 

 can easily be seen in any germinating seed (see fig. 21 b, 

 d, e) . We notice in it a leaf -bud and the beginning of a 

 root. The remaining larger portion of the seed is filled 

 with a white, uniform, mealy mass, called the endosperm 



Fig. 20. 



