VARIATION OF THE CARBOHYDRATE-FACTOR 219 



It is quite probable that, in the complex process of 

 photosynthesis, carbohydrates are produced other than those 

 just referred to. Accurate determination of variation of 

 the carbohydrate-factor under change of external conditions 

 will no doubt lead to a clearer insight into the chemical 

 side of the problem. However, the following investigations 

 show that the value of the factor is modified in a definite 

 relation to the intensity of the light to which the plant 

 had been previously exposed. I select the two extreme 

 cases, those of excessively strong light and of semi-darkness. 

 I will now describe the effect of these in modification of the 

 carbohydrate-factor. 



Carbohydrate-Factor of Specimens grown in 



Sunlit Pond 



All these specimens were found to be overloaded with 



starch. The following is a detailed account of a typical 



experiment continued from 8 a.m. to 4 p.m. under exposure 



to bright light from the sky. The volume of evolved 



oxygen measured at 21 C. and pressure of 766-6 mm. was 



found to be i-oo c.c; reduced to N.T.P. it was 0-914 c.c, 



the weight being 1-316 mg. The observed increase of 



weight of the leaf due to production of carbohydrate was 



1 • 20 mg. The oxygen-carbohydrate factor was therefore 



1 - 20 



=o-qi, which is 2 per cent, higher than the value 



1-316 



(0-89) in normal specimens. Six others from the same 



pond gave likewise a higher value for the factor. This 



indicates that in plants kept in strong light the production 



of glucose is relatively the greater. 



Carbohydrate-Factor of Specimens Previously 

 Subjected to Semi-Darkness 



For the following investigation I took a specimen from 

 the sunlit pond, and kept it in a semi-dark room for two 

 days, during which the starch-content was reduced below. 



