12 



Lewis Knudson 



cultures in the dark through a period of a few days. Neither glycogen, 

 dextrins, nor soluble starch were utilized. While the experiment was not 

 conducted under sterile conditions, the conclusions need not be questioned 

 because of the fact that the starch accumulated in the leaves when the plants 

 were maintained in the dark and because the duration of the experiments 

 was short. 



Maze (1899) grew vetch (vesces de Narbonne) under sterile conditions 

 in the dark, supphdng to the solution different quantities of glucose. 

 Some of his data follow : 



Duration 

 (days) 



Glucose 



(parts 



per 100) 



Dry 



weight 



of plant 



(milligrams) 



Dry 



weight 



of seed 



(milligrams) 



Gain or 

 loss 

 (milli- 

 grams) 



50 



39 



92 



92 



53 



1 

 2 

 4 

 6 

 



269.0 

 276.7 

 838.2 

 710.0 

 161.6 



202.8 

 202.8 

 202.8 

 202.8 

 202.8 



+ 66.2 

 + 73.9 

 +635.4 



+507.2 

 — 41.2 



With 4 per cent and 6 per cent of glucose the plants grown in the dark 

 more than trebled in dry weight, while in the absence of sugar there was 

 a loss of weight. 



The work of J. Laurent (1904) is particularly noteworthy. He grew 

 plants in water cultures under sterile conditions. His conclusions, par- 

 ticularly with respect to the utihzation of sugar by corn, are as follows: 

 (1) With glucose present in the nutrient solution there is an increase in 

 growth and an increase in drj^ weight. (2) Glucose is utilized if the 

 plant is grown either under conditions of darkness or in the light, and 

 in the absence of carbon dioxide as well as under normal conditions. 

 Saccharose, glycerin, and potassium humate are also utilized. The 

 saccharose is inverted in the root by the enzyme invertase. This sugar is 

 also transformed in slight amounts in the culture solution, due to the 

 secretion of invertase. The same is true for peas. Starch supplied to the 

 nutrient solution is partially utilized, due to the exosmosis of diastase from 

 the seed and its action on the supplied starch. (3) Glucose is absorbed by 



