308 



Plant Physiology 



other is a change in internal structure, either within the 

 cell, or affecting groups of cells, resulting in differentiation. 

 Extension is evident, and differentiation may be obscure ; 

 when the flower is fully open, for example, growth processes 

 may go on within, which may or may not result in evident 

 increase in size or weight, but new and important structures 

 may be formed, and there is growth. Just so there is no 



FIG. 78. A potato sprouting in a dry, hot atmosphere, and in strong 



light. 



increase in the size of the incubating hen's egg, but by 

 growth the little chick is soon developed from the simple 

 fertile egg cell, with its stored food-material. 



177. Growth of the embryo. Growth of the embryo 

 (Fig. 79) in plants has been nowhere more carefully studied 

 than in certain of the crucifers, notably in Capsella Bursa- 

 Pastoris, a classical example among dicotyledons, which 



