344 



The Living Plant 



even in structures which grow on continuously, and in which it 

 would seem that the two phases must be mixed up together, they 

 are separated in space, although not in time. Thus, in roots, the 

 development of new cells occurs in the growing point (figure 53, 

 139, D), while the enlargement of cells to full size takes place in the 



Fig. 131. — A Castor Bean plant, with its dry substance in a vial alongside. (The vial, of 

 course, was photographed later, and worked into the plate.) 



zone just behind, a fact which explains the enlargement of that 

 zone as shown in our earlier figures. The same is true likewise of 

 the stem, though less strikingly. Moreover, it is also a very inter- 

 esting fact that if a plant is suddenly called upon to increase be- 

 yond the normal, as for example in the longer leaf-stalks demanded 

 of water plants forced to grow in deeper water, or in the leaves of 

 plants whose buds have all been destroyed, the enlargement is 



