10 BULLETIN 1053, U. S. DEPARTMENT OF AGRICULTURE. 
germination was lower. In three days" the mycelium from the spores 
kept in the dark was more advanced than that from the spores ex- 
posed to the sunlight. Rhoads (47, p. 66) noted no difference in the 
time required for the germination of the spores of Polyporus paryu- 
menus in the presence or absence of diffused light. 
The writer tested the action of both diffused light and direct sun- 
light upon dry spore prints for a possible killing effect and upon 
spores on agar during germination for a possible inhibiting effect. 
Duplicate spore prints upon slides or agar plates with spores for 
germination were placed side by side in the light, supported upon 
a nonconducting frame, with one of the pair inclosed in a box made 
light-tight- and yet allowing for ventilation, in order to prevent the 
heating of the slides or Petri dishes. Experiments upon the effect 
of diffused light acting during germination were started in the early 
morning and allowed to run until the next night, in order to have 
the spores under the influence of light while starting to germinate 
and to obtain the maximum amount of daylight. 
It was found that two days of diffused light in an east window 
during the winter had no appreciable effect upon the percentage of 
germination or upon the rapidity of germination, although it hin- 
dered the subsequent growth of the thalli somewhat. 
It was found also that diffused light acting upon dry spore prints 
for 10 days had no appreciable effect on the viability of the spores. 
Direct sunlight acting upon the basidiospores upon agar inhibited 
germination during exposure, as compared with controls. Spores 
exposed to direct sunlight for one day would germinate upon being 
set aside in the dark, but those exposed for two days showed little 
or no germination. 
The tests on the killing effect of direct May and June sunlight 
upon dry spores were carried on chiefly with the basidiospores of 
Lenzites sepiaria and L. trabea, with two tests on the spores of 
Trametes serialis and Lentinus lepideus. When the tests were prop- 
erly Checked so as to obviate as far as possible the effect of atmos- 
pheric conditions, the results were as consistent as could be expected. 
In general, it was found that one day of exposure did not affect 
the viability of the spores materially. An exposure of two days 
usually reduced the percentage of germination considerably, some- 
times entirely, while three days' exposure usually killed most of the 
spores. Only those tests were considered in which the control slides 
showed unreduced germination at the end of the test, for it was 
found, as will be shown later, that certain atmospheric conditions 
greatly reduced the viability of the spores. 
Two experiments were tried to see if the germ tubes showed any 
phototropic reactions. The slides of Van Tiegham cells were placed 
