Study of Spirogyra mtida. 247 



we may readily suppose that free oxygen, in greater quan- 

 tity than is supplied by still water, is necessary in order 

 that it may produce hydrolyzed products from starch. 



The Action of Light on Diastask. 



A consideration of the foregoing results led to an inves- 

 tigation of the behavior of unorganized hydrolytic fer- 

 ments in rays of varying refrangibility. The information 

 which we possess upon this point is very limited, and its 

 relation to plant metabolism is quite untouched. 



St. Victor and Corvisart * state that sugar is formed 

 from starch more rapidly in light than in darkness. 

 Green f exposed solutions of diastase to the action of 

 electric light and of sunlight. The diastase so treated 

 was then allowed to act upon starch paste, when he found 

 that light exercised a destructive influence upon the fer- 

 ment, this influence being more marked at the violet end 

 of the spectrum. But the light with which he experi- 

 mented was polychromatic, and if diastase is affected by 

 light rays, it is probable that the portions of the spectrum 

 affecting plant growth will also influence the rapidity of 

 diastatic action. J 



The relation of light rays to the ferment is, as deter- 

 mined by the previously described color screens, very 

 marked, and in perfect accord with the changes observed in 

 Spirogyra when grown under corresponding conditions. 

 An account of the experiments whereby this conclusion 

 has been reached, will make clear the above statement. 



Potato starch was purified by washing with very dilute 

 potassium hydrate, then with 1 per cent, hydrochloric 



*Cotnptes Rend., Vol. 49. f Annals of Botany, Vol. 8. 



X After this investigation had been passed to press another article by 

 J. R. Green appeared in the Proceedings of the Royal Society, Vol. 61, 

 p. 25. Many of his results agree with those above given, but some are 

 strikingly different. In the above investigation narrower, and therefore 

 purer, colored bands were used than those from which Green drew his 

 conclusions. It is noticeable that he fails to give the action of the yellow 

 rays as distinct from the orange. 



