ASSIMILATION OF CARBON BY PLANTS 



199 



from 5800 to 7600 A. and higher; that is why electric hght 

 appears somewhat yellow to the eye. 



As photosynthesis is most intense in the orange-red region of 

 the spectrum, the composition of artificial light is sufficiently 

 favorable for the assimilation of carbon dioxide by the plants. 

 But as it is poor in blue- violet rays, the processes of the formation 



Fig. 60. 



-First cabbage and clover plants ever grown entirely in artificial light; 

 used for carbohydrate analysis (after Harvey). 



of organs deviate from their normal course in that the stems 

 elongate excessively, the leaves on the contrary remaining insuffi- 

 ciently developed. Elongation is also favored by the abundance 

 of infrared rays, which cause increased heating of the plants. 



It must be mentioned that great divergencies exist among 

 various kinds and groups of plants in their relation to the compo- 

 sition of light. Many crop plants, e.g., wheat and other cereals, 



