384 BOTANICAL GAZETTE [MAY 
carbohydrates, only a slight increase in length occurs, probably 
at the expense of carbohydrate originally present in the root tip. 
Glucose is apparently a better source of carbon than levulose 
for all three plants and for both tops and roots. This is particularly 
Fic. 4.—(1) Corn shoot tips grown in dark in Pfeffer’s solution plus 2 per cent 
levulose; (2) plus no carbohydrate; (3) plus 2 per cent glucose; (4) pea shoot tips grown 
in dark in Pfeffer’s ema he 2 per cent levulose; (5) plus 2 per cent glucose; 
(6) plus no carbohydra 
noteworthy in the case of cotton, where the increase in length ol 
the root tips in glucose, as indicated in table III, was thirteen times 
the gain in levulose, twice as many secondary roots were produced, 
