246 Pennington — A Chemico-PJiysiological 



Fresh Spirogyra was next placed in a flask fitted with a 

 doubly perforated cork carrying glass tubes arranged as in 

 an ordinary wash bottle. The short tube was connected 

 with a suction pump, and by means of the long tube a cur- 

 rent of air was drawn through the flask. The air must not be 

 drawn through with such force that it churns the Spirogyra 

 in its passage. If the flask is kept quite dark, the plant 

 under such treatment behaves precisely as it does when 

 running water is supplied to it ; the starch is rapidly meta- 

 bolized, and the cells soon become starch free. 



From the above facts we are led to believe that in this 

 starch transformation the gases of the air play an import- 

 ant part. Since all experiments have shown that carbon 

 dioxide is acted upon by chlorophyll only when light is 

 present, we must look to the oxygen as the active agent. 

 This element seemed, by its presence, to so stimulate cer- 

 tain functions of the cell that it was enabled to convert 

 starch into soluble products. 



An explanation of this peculiar behavior lies in the fact 

 that the simpler nitrogenous substances, such as amides, 

 are built up in the dark, and that these substances there 

 unite with the carbohydrate present, to form the more com- 

 plex compounds or proteids. 



While the absorption of free oxygen by the plant is 

 generally followed by a breaking down of the organic sub- 

 stances, just as in animal respiration, it is probable that 

 being deprived of the nascent oxygen, which results from 

 the decomposition of carbon dioxide in sunlight, and also 

 from the free oxygen of the air or water, the plant is un- 

 able to combine the first-formed nitrogenous compounds 

 with the carbohydrate already present. Or, since we know 

 that in time the starch is dissolved, this synthesis takes 

 place so slowly that the equilibrium of the cell is destroyed 

 before all the carbohydrate is used by the nitrogen com- 

 pound. 



The nature of the hydrolytic ferment in Spirogyra is as 

 yet unknown. But from the study of this class of ferments 



