GERMINATION OF A SEED 



21 



others its quiescence takes place very early, so that the 

 endosperm remains unabsorbed around it and is not 

 used till the resumption of active life and growth takes 

 place. The difference in the time of this absorption 

 influences the size of the embryo, which is naturally 

 much larger when it has absorbed the endosperm. The 

 food so absorbed is always deposited again in some part 

 of the young embryo, very frequently in the cotyledons 

 which become large and fleshy. Occasionally, as in the 

 Brazil nut, it is stored in the axis of the embryo. . 



When the endosperm persists till the resumption of 

 life by the embryo the process known as 

 the germination of the seed the latter is 

 said to be an albuminous seed (Fig. 6). If 

 the embryo alone is present inside the skin 

 (Fig. 7) it is called exalbuminous. 



It is best to begin the study of these 

 seedbearing plants with the largest group, 

 the Dicotyledons. 



They furnish us with examples of both classes of 

 seeds which are easily accessible and which germinate 

 readily. We may take first the 

 common bean. To examine the 

 seed it is well to soak it for 

 several hours in water, which 

 is absorbed by the skin, so that 

 the whole seed swells and its 



FIG. 7. Embryo of pea parts can be easily separated 

 magnified, r, radicle; nt, f rom one another. The seed is 



plumule; c, cotyledons. . . . , . 



somewhat kidney - shaped, and 



bears on the concave part a scar at the point at which 

 it was attached to the fruit from which it came. A 

 little way from one end of this scar is found an 

 aperture through the skin, known as the micropyle, 

 through which the radicle emerges on germination. It 

 can be localised by gently squeezing the soaked seed, 



a, embryo. 



