146 Trow . — Observations on the Biology and 
Professor Klebs, the effect of a high temperature was first 
tested : sixteen-day cultures were placed in a water-bath 
which was kept at a constant temperature of 29 0 C. in the 
dark for five days. There was no appreciable effect : not 
a single spore germinated. The same cultures, however, 
yielded valuable material six days later, after having been 
placed in a south window exposed to the full benefit of such 
sunlight as was afforded by a wet week in September. 
Cover-glass cultures were not checked in their development 
on being placed in this bath, so that we may conclude that 
this treatment had neither a stimulating effect upon the 
resting spores nor an inhibitory action upon those already in 
process of germination. 
Another experiment which produced negative results was 
carried out as follows: — Eighteen-day cultures were kept at 
o° C. in ice for fifty-two hours and then transferred to a warm 
well-lighted greenhouse at 6 5 0 F. to 70° F. for sixty-four hours. 
Here again exposure in the south window brought about free 
germination in the course of ten days. It appeared as if 
a combination of bright light and a high temperature would 
have a stimulating effect. Accordingly a sixteen-day culture 
was placed near a water-bath close to a very strong incandes- 
cent lamp : the temperature was maintained during constant 
illumination at 3 2° C. for forty-four hours: no spores 
germinated. On examination seven days later, after exposure 
in the south window a few germinating oospores only were 
found. Cover-glass cultures in a dimly lighted room gave 
the best results in germination, so that no experiments were 
set up to test the effect of bright light alone. A good supply 
of oxygen is probably a factor of great importance. 
It may be noted further that the course of development, 
apart from the germination of the spores which has not yet 
been adequately tested, is perfectly normal in both ordinary 
or moist-chamber cultures whether these are exposed to, or 
protected from, the influence of light. In proof of this it 
may be stated that appropriate cultures carried out side by 
side with the external conditions exactly alike, but differing 
