104 



REGENERATION 



The increase in the shoots produced from the descending sap 

 from the apical leaf increased with the mass of the apical leaves, 

 but less rapidly. (The mass of the basal roots increased, 

 however, almost in direct proportion with the mass of the leaf.) 



Part of the material sent out by the leaf in the descending 

 current seems to be utihzed for the growth in length and thickness 

 of the more peripheral tissues of the stem from which the roots 

 originate, leaving only a fraction of the material of the descending 

 current free to be utilized for the growth of the shoots in h and c 



Fig. 81. — Stems split longitudinally from apex almost to the base. Stem b, 

 with one apical leaf, forms a shoot with greater mass than the stem a, without 

 leaf. In stem b the shoot formation is suppressed on the side where the apical 

 leaf is. Root formation in b first on side of leaf. Jan. 12 to Feb. 8, 1923. 



of Fig. 80. This would explain why the mass of shoots formed in 

 the basal parts of a stem cannot increase in direct proportion with 

 the mass of the apical leaf. 



That the descending current from a leaf carries material that 

 can be utihzed for shoot formation can also be demonstrated in 

 the following form of experiment: 



In Fig. 81 the two stems a and b are split longitudinally from 

 the apex down to near the base which dips into water. Stem a 

 has no leaf while stem h has an apical leaf to the right. The 



