THE 



AMERICAN 

 JOURNAL OF SCIENCE, &c. 



Art. I. — On the Action of Yellow Light in producing the Green 

 Color, and Indigo Light the Movements of Plants ; by D. P. 

 Gardner, M. D., Cor. Memb. Lye. Nat. Hist. New York. 



(1.) The object of this paper is to prove the existence of dif- 

 ferent properties in the rays of the spectrum, in their action on 

 vegetables ; and more especially to show that the rays which 

 produce the green color of plants, are altogether dissimilar from 

 those which influence their movements towards light — the color 

 being developed by the less refrangible rays, and chiefly by the 

 yelloxo ; whereas, the motion is influenced by indigo light. The 

 discussion of the subject will be divided under three heads: 



1. On the production of chlorophyl by yellow light. 



2. On the movements of plants towards indigo light. 



3. Some application of these facts to vegetable physiology. 



I. On the production of chlorophyl by yellow light. 



(2.) It is a fundamental fact in botany that light is necessary 

 to the formation of chlorophyl. Von Humboldt adduced certain 

 exceptions to this law, in the case of plants found in the mines 

 of Freyberg, and with Senebier ascribed the green matter to the 

 action of hydrogen gas. But the experiments of the latter failed 

 in the hands of De Candolle, and a series instituted by myself, 

 and conducted with great care, were equally unsuccessful. On 

 the other hand, Humboldt succeeded in greening a plant of Le- 



Vol. xlvi, No. 1.— Oct.-Dec. 1843. 1 



