ENDOTHIA PARASITICA AND RELATED SPECIES, 43 
LIGHT RELATIONS. 
The relation of light to pycnospore production in E'ndothia para- 
sitica was first discussed by Anderson (1, p. 20). He says— 
When plate cultures are grown in total darkness on chestnut-bark agar, no 
pycnidia are developed, while on plates made at the same time and grown 
in the light, the usual rings of pycnidia appear (fig. 57). Experiments were 
also tried in which the plate was left in darkness until about half covered 
with mycelium and then brought into the light. Circles of pycnidia were 
developed, beginning with the ring which marked the outermost limit of the 
colony when removed from the dark chamber. The concentric rings which 
always appear on agar cultures are due to the alternation of night and day. 
Later, in a bulletin by Anderson and Rankin (6, p. 592), the same 
results are attributed to D. C. Babcock. 
Up to the time the above-mentioned work was published the 
writers had grown about 3,000 cultures of the several species of: 
Endothia on various media in flasks and tubes. Practically all of 
these cultures had been kept in dark cases and Endothia parasitica 
had produced pycnidia abundantly on most of the media used. It 
seemed desirable, therefore, to determine whether wholly different 
light relations existed when the fungus was grown on plates. The 
following series of tests was accordingly made, using /. parasitica 
only. 
LIGHT TESTS OF CULTURES ON PLATES, 
In experimenting with plate cultures in order to check up the 
results reported by Anderson and Rankin (6, p. 592) it was noted 
that there was great variation in the rate at which the cultures 
dried out. There was considerable variation in this respect in dif- 
ferent plates kept side by side, apparently due to differences in the 
Petri dishes, and a marked difference between cultures kept in 
light and those kept in darkness. Since a causal relation between 
lack of moisture and abundant spore production had already been 
shown, it seemed probable that this might influence the results of 
the light tests in plate cultures. In fact, in a few cases the cultures 
kept in the light did produce spores earlier than those kept in dark- 
ness. Accordingly, in order to eliminate at least in part this fact 
which seemed to obscure the possible effect. of light, a method was 
sought of equalizing the loss of moisture. Tn the following series 
half the plates were placed under a plain bell jar and the other half 
under a bell jar of equal size but darkened by being covered inside 
and out with heavy black paper, such as is used to wrap photographic 
plates. The two bell jars were then set side by side in front of a 
north window. By this means the conditions were made much more 
uniform as to temperature and moisture. There was still a slight 
difference in the rate of drying and undoubtedly at times a difference 
