The Royal Society, London. 



375 



Effects of light. 



Number 



of experi- 



ment. 



Conditions of 

 experiment. 



Result. 



Remarks. 



Poor Hght; no sun 



10a 

 106 



11 



12a 



126 



13 



14 



19a 



166 



Light passing through 



yellow glass 

 Light passing through a 



Solution of potassium 



Chromate 

 Light passiug through red 



glass 

 Light passing through 



blue glass 

 Light passing through a 



Solution of copper sul- 



phate and ammonia 

 Light passing through 



green glass 

 Light passing through 



whitewashed glass 

 Plant in darknesa in a 



greenhouse 

 Plant in darkness under a 



zinc cylinder in the open. 



No outgrowths 



formed 

 Outgrowths 



formed 



No outgrowths 

 formed 



Outgrowths 



formed 

 No outgrowths 



formed 



Effects of temperature. 



The formation of outgrowths (provided there is adequate moisture 

 and light) is promoted by a high temperature. 



3. They only occur (ceteris paribus) in plante in which there 

 is an accumulation of starch. 



4. They are formed under clear glass and under red and yellow 

 glass, but not under blue or green glass, and in no case in 

 darkness. 



5. Their formation is accompanied by the production of oil, which 

 is not found in normal leaves. 



6. The presence of this oil suggests that events similar to those 

 occuring in succulent plants are taking place, viz. 7 reduced 

 respiration and the development of osmoticaily active substances 

 in excess. 



7. It is therefore probable that the intumescences are due to the 

 local accumulation of osmoticaily active substances, produced 

 under the abnormal conditions, viz., reduced transpiration and 

 consequent lack of minerals, while carbohydrates are being deve- 

 loped in excess. 



