1918] ROBBINS—ASSIMILATION OF CARBON 545 
glucose. The heavy dark green mat formed on the glucose agar 
is shown in fig. 1. This photograph was made 1 month after 
inoculation. 
In solution cultures the utilization of the glucose was shown 
even more clearly. Fifty cc. of Czapek’s nutrient solution for 
fungi (2) plus o.1 gm. of calcium chloride per liter was placed 
in 125 cc. Erlenmeyer flasks. To some of the flasks 3 per cent 
glucose was added. All were sterilized and inoculated with the 
lanes Seal 
—, ie 
Fic. 2 
GS. 1, 2.—Fig. 1, Ceratodon purpureus grown 1 month in light on nutrient 
ar: 2 tubes to left stele no glucose; 2 tubes to right contain glucose; fig. 2, 
8 
Ceratodon pur pureus grown in dark for 1 month in modified Czapek’s sobition: flask 
to left contains 3 per cent glucose; flask to right contains no organic compound 
moss by transferring a bit of the protonema growing on agar in a 
test tube. Some of the flasks were placed in a north window and 
others in a dark cupboard. At the end of a month and a half it 
was found that in the light far more growth had occurred in the 
flasks containing glucose. In the glucose solution only protonema 
had developed; in the check young moss plants had been formed. 
In the dark no growth had occurred in the check, while the solutions 
in those flasks containing glucose were completely filled with a 
mass of dark reddish brown colored protonema (fig. 2). 
AVAILABILITY OF DIFFERENT FORMS OF CARBON.—The culture 
solution used was one devised by Moore for the culture of algae, 
