686 LIGHT AND LIFE 



agents and light. It is therefore unfortunate that work with these 

 plants was started so recently. Had they been studied as long as 

 Xanthium, Hyoscyamus, or Perilla, for example, the mechanism of 

 photoperiodism would surely be better known than it is. There is no 

 reason to believe that the Lemnaceae are less "typical" of higher plants 

 in metabolism and responses than those mentioned, or to treat them 

 as botanical curiosities. Only their gross morphology, size, and per- 

 haps the resulting ease with which applied substances can be taken up, 

 constitute the difference, making them experimental organisms with 

 many of the advantages of those other curiosities, Drosophila and 

 Neurospora. 



Acknowledgment 



This work was supported by National Science Foundation grant G-4433 to 

 A. W. Galston. 



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