548 BOTANICAL GAZETTE [JUNE 
effects of glucose, levulose, and maltose on the moss are shown in 
figs. 3 and 4. The cultures also differed in color. The protonema 
in the levulose, glucose, and cane sugar was brownish at the end 
of the experiment; while in the lactose, maltose, and check it was 
still a normal green. 
COMPARISON OF LEVULOSE AND GLUCOSE AS CARBON SOURCES.— 
In the preceding experiment the growth when levulose was the source 
of carbon was so much greater in amount (fig. 5) than that when 
glucose was the source of carbon that a further comparison of 
the effects of the two sugars was made. The moss was grown from 
Fic. 5.—Ceratodon tales grown in dark for 2 months in nutrient solution: 
from left to right, o.1 mol. levulose, no carbohydrate, o.1 mol. glucose. 
November 27 to February 24 in the modified Czapek’s solution 
mentioned. Triplicate cultures were grown in the light and in 
the dark. The dry weight of the moss was determined by filtering 
the protonema and moss plants into a Gooch crucible and drying 
at 110 C. The sugar determinations were made by the use of 
Fehling’s solution. The results are given in table II and represent 
the averages of the data for triplicate cultures. 
The sugar analyses given in table II show an unmistakable con- 
sumption of sugar in all cases. More levulose was used than 
glucose. In the case of levulose the greater consumption of sugar 
occurred in the dark. In the case of glucose the greater consump- 
tion occurred in the light. Comparing the dry weights of the 
moss protonema and plants in the check, glucose, and levulose 
solutions, it is evident that the sugar has greatly increased the 
