INHIBITORY EFFECTS OF A SECOND ORDER 



121 



apical leaf for shoot formation will be the less, the farther the sap 

 has to travel down the leaf, the ratio being as follows : 



One gram of leaf produces 107 milligrams dry weight of shoots 



in node 0. 

 One gram of leaf produces 56 milligrams dry weight of shoots 



in node 2. 

 One gram of leaf produces 36 milligrams dry weight of shoots 



in node 4. 



Fig. 97.— Half stem with leaf at base. Nov. 12 to Dec. 5, 1923. 



The simplest explanation for this difference seems to be that in 

 young stems, which are still in the process of vigorous growth, 

 material of the descending sap is retained or consumed in the 

 stem (for the growth of the stem?) and that for this reason the 

 material available for shoot formation by the descending sap 

 from the apical leaf diminishes with increasing distance of the 

 seat of shoot formation from the leaf. 



