68 LIGHT, VEGETATION AND CHLOROPHYLL 



in the proportions indicated, which seems certain in many 

 cases, then the evaporation of a large quantity of water is 

 vitally important. 



The abundance of infra-red radiation normally provokes 

 intense transpiration, but what happenes when the quantity 

 of water available to the plant is insufficient, or when the air 

 surrounding the leaves is so charged with moisture that 

 evaporation is checked? 



The leaves then become damaged and the plant withers; 

 experiments have given this result in conditions of high 

 temperature, strong infra-red illumination and very moist 

 air existing simultaneously. 



Gathered fruit and melons deprived of their leaves as a 

 result of disease, and therefore incapable of evaporating 

 water, suffer from scorching under the action of intense 

 radiation. 



These effects have been observed, but it is not known 

 whether intense visible radiation deprived of infra-red would 

 not be capable of causing the same disorders, since, in 

 ordinary natural conditions, the visible and the infra-red 

 always come together. 



