THE METABOLISM OF PLANTS, 

 i. Complete daily period in Euphorbia Lathy r is : 



2. Time of occurrence of maximum temperature in various plants 



It is generally admitted that this daily periodicity is 

 entirely due to causes inherent in the plant, to variations in 

 the activity of its destructive metabolism. It is, however, 

 affected by variations, in the external conditions. The evolu- 

 tion of heat by the plant is greater when the external 



