72 



REGENERATION 



Fig. 53. — Stem split longitudinally, each half with leaf in middle. Left, 

 whole leaf; right, more than half of leaf cut ofT. Root and shoot production in 

 the two pieces of stem increases with mass of leaf. 



If account is taken of the fact that part of the material sent by 

 the leaf into the stem is consumed for the growth of the latter 

 (as was shown in Chapter VI), the mass of shoots produced in 

 the stem varies approximately with the mass of the leaf. 



In these experiments the base of the stem dipped into water 

 and it might be argued that the substances taken by the stem 

 therefrom and carried in the ascending sap might have had a 

 share in this result. For this reason the experiments were 

 repeated on stems suspended entirely in moist air. The result 

 was essentially the same. 



