Light 323 



tion. Specific photoperiodic reactions have been found to be gene-con- 

 trolled. The.morphogenetic effects of bright light and of limited water 

 supply are sometimes hard to disentangle. It is difficult, as has been 

 said before, to separate any one factor sharply from the others and to 

 study it in isolation. All are concerned with the entire organized system 

 that is the plant. 



