Journal of Agricultural Research 
Vol. XXV, No. 3 
158 
enzym secreted into the solution, (3) the dry weight of fungous materials- 
produced, (4) fruiting, and (5) the amount of glucose consumed. 
The methods employed in these experiments are briefly as follows: 
Czapek’s modified nutrient solution (15) was employed, using 20 per 
cent dextrose as a source of carbon. Thirty cc. of this solution were 
placed in each of 210 100-cc. Frlenmeyer flasks, 100 of which, after 
being inoculated, were held in the dark; 100 were inoculated and held 
in the light; and 10 were left uninoculated as controls. The flasks were 
all placed on a laboratory table near a north window. A wooden frame 
was placed over each set of 100 flasks. The flasks in the dark were- 
covered with three thicknesses of a good grade of satine, and held in 
place on the top by means of plate glass. Air was admitted at the sides, 
and the light excluded by packing the black cloth closely against the 
flasks. The top of the frame over the flasks in the light was covered 
only by the plate glass but the sides were wrapped with white cloth,, 
making them in every way comparable to the sides of the rack covered 
with black cloth except for the color of the cloth, thus affording the same 
opportunity for aeration and temperature fluctuations in both sets. 
Twenty flasks of each set were removed at the end of 3, 4, 5, 6, and 7 
days. The solution from each set was combined into one sample. 
The sugar present in this sample was determined by means of a Fric 
saccharimeter. Another portion of the solution was utilized in macera¬ 
tion tests according to methods detailed elsewhere (4). The mycelium 
from each set, after being washed carefully in running water, was col¬ 
lected into one crucible and its dry weight determined. The results 
from duplicate experiments are shown in Tables II and III. 
An examination of Tables II and III reveals no material difference in 
the results obtained which might be attributed to the influence of light. 
There was a slight difference in fruiting, but this was not marked. It 
is interesting to note in this connection that other investigators have 
found that there is no general agreement among fungi with respect to 
the influence of light on their growth and fruiting. Lendner (7) found 
considerable disagreement among different members of the Mucorineae 
and some of the conidial forms of the ascomycetes, while Levin (8) 
showed that total darkness completely suppressed the formation of or 
greatly reduced the production of pycnidia in some of the Sphaeropsi- 
dales. Investigations in still another group of fungi (Agaricaceae) by 
Maire and de Laroquette (jo) indicated that here also light has no con¬ 
stant influence on fructification. 
The hydrogen-ion concentration of the solutions was considerably 
increased and the results show that the acid present was sufficient ta 
cause dissolution of the middle lamellae. It was found that after some 
of the solution on which the fungus had grown was neutralized by the 
addition of NaOH, it no longer macerated raw disks. There was no 
difference in the time required to macerate raw sweet-potato disks in 
the steamed and unsteamed solutions on which the fungus had grown. 
It will also be seen that there was no maceration in the control solutions, 
or in the solutions in which the fungus had grown. It seems quite evi¬ 
dent from these results that no pectinase was formed, otherwise there 
would have been some difference in the time required to macerate the 
disks in the steamed and unsteamed inoculated solutions. What 
maceration took place in the solutions must be attributed wholly to the 
acid or to some other substance besides an enzym. 
