ISOLATED LEAVES OF BRYOPHYLLUM 



17 



We may, therefore, draw the conclusion that the quantity 

 of regeneration of a detached leaf of Bryophyllum (measured 



In dark 



In light a^ 



Fig. 18. — Influence of light on mass of shoot and root production from detached 

 leaves, one leaf a kept in dark, sister leaf a\ kept in light. The mass of shoot 

 and root production in the dark is only a small fraction of that in light. Mar. 

 13 to Apr. 4, 1923. 



in dry weight of regenerated organs) under the influence of 

 light is determined chiefly by the mass of material produced by 

 assimilation. 



Table V 



Not all the material formed under the influence of hght in a 

 leaf is utiUzed for the formation of roots or shoots; part of the 

 material may be used for the growth of the leaf itself. This was 

 shown in the following way: 



Six pairs of sister leaves were cut off from plants. Each of the 

 two sets of leaves had almost equal wet weight at the beginning. 

 Six leaves were put into the drying oven at once to determine the 

 dry weight at the start of the experiment. The 6 sister leaves 

 were suspended in an aquarium, their apices dipping into water. 

 At the apex, regeneration took place. Twenty-nine days later, 

 after a considerable mass of roots and shoots had developed, 



