CONSTANT VALUE OF OXYGEN-CARBOHYDRATE FACTOR 217 



Table XXXI. — 'Determination of Increase of Weight due to 

 Photosynthesis by Indirect and Direct Methods 



The agreement found between the calculated value and 

 the actual increase of weight is so remarkable as to justify 

 the conclusions (1) that the oxygen-carbohydrate factor in 

 normal Hydrilla plants under given conditions is definite ; 

 and (2) that the increase of weight can be accurately determined 

 by multiplying the weight of oxygen evolved by the oxygen- 

 carbohydrate factor. 



Though this factor is constant in normal specimens, 

 I will presently describe experiments which show that 

 it undergoes a definite variation under changed conditions 

 in regard to the intensity of light to which the plant had 

 been habitually exposed. It is a matter of interest and 

 importance to ascertain the significance of the constant 

 factor and its variation under definite external conditions. 



It is commonly assumed that the first formed carbo- 

 hydrate is a hexose glucose, and that its formation may be 

 generally represented by an equation such as the following : 



6C0 2 + 6H 2 = C 6 H 12 6 + 60 2 



On this assumption the oxygen-carbohydrate factor 



will be 



glucose C 6 H 12 0« 180 



oxygen 60 2 192 



= T — = °-9375 



But in no case was the value of the factor found to be 

 so great as this : in normal specimens the observed value 

 of the factor 0-8906 is 5 per cent, less than this calculated 



