JACQUES LOEB 307 



1.891 represents the gain in mass of the stem. We therefore find 



that a = 1.803, and that ai -\- hi — h = 1.891. The ratio of 



a 

 ;; 7 should be = 1. In our experiments it is = 0.95, which 



is as near the theoretical value as the accuracy of our experiments 

 permits. 



We, therefore, can state: When a leaf is connected with a piece of 

 stem the stem gains in weight and this gain equals the weight of roots 

 and of shoots formed by the sister leaves detached from the stem. 

 The inhibitory effect of the stem upon shoot and root formation by 

 the leaf is therefore adequately explained by these figures as being 

 due to the fact that the material available for growth normally flows 

 from the leaf into the stem. 



SUM MA RY. 



1. Equal masses of sister leaves of Bryophyllum calycinum pro- 

 duce equal masses of shoots and roots in equal time and under 

 equal conditions. 



2. The mass of shoots and roots produced by different masses of 

 sister leaves in equal time and under equal conditions is approxi- 

 mately in direct proportion to the masses of the leaves. 



3. When a piece of stem inhibits the production of shoots and 

 roots in a leaf of Bryophyllum connected with it, the stem gains in 

 mass and this gain in mass equals approximately the mass of shoots 

 and roots the leaf would have produced if it had been detached from 

 the stem. 



4. This suggests that the inhibitory influence of the stem upon the 

 formation of shoots and roots in the leaf is due to the fact that the 

 material available for this process naturally flows into the stem. 



