Jan. 17, 1916 
Plenodomus fuscomaculans 
727 
which was designed especially for this work seems free from this criti¬ 
cism, since cultures placed in it before icing began developed pycnidia. 
This incubator had two openings (i-inch diameter) to the outside and 
a small fan, driven by a motor, which continuously brought about good 
aeration and prevented fogging of the doors. The constancy of tem¬ 
perature during the first week can be vouched for within the limits set, 
and for the next month no large deviation occurred. 
The lack of apparatus to give constant temperatures, and at the same 
time illumination and aeration, prevented any further experimentation 
along this line. Pycnidia have been obtained in cultures with a tem¬ 
perature range of from io° to 30° C. No pycnidia were obtained at 6° C. 
and no other inhibiting factor than temperature is known to have en¬ 
tered. The experiments with the constant-temperature incubators are 
disregarded because of the entrance of other factors, but are included 
merely to show the difficulty of experimenting with this factor. 
The wide limits of pycnidium production, so far as temperature is 
concerned, allowed great leeway in experimentation; but outside these 
limits temperature may show as marked an effect as light. It is note¬ 
worthy that growth shows wider temperature limits than reproduction. 
AERATION 
The oxygen relation is no doubt the most essential of all life relations, 
and the statement “No life without air” has been shown to be universal, 
the contributions of Beijerinck (1893), as well as those of Termi and 
Bassu (1904, 1905), showing that even the strictest of known anaerobes 
require minute traces of free oxygen. The relation of oxygen to plants 
was recognized almost from the beginning, but the interpretation of 
respiration by Pfeffer (1889) is fundamental. In this we have respira¬ 
tion portrayed as the energy-releasing process. Subsequent work has 
dealt with the effect of various external conditions upon the respiratory 
quotient. Necessarily all respiration relations depend upon the quality 
of the nutrition as well as the quantity of nutrients. The general con¬ 
clusion which has been expressed by Beijerinck (1899), that all plants 
have a definite oxygen optimum and that aerobes are those whose optimum 
is high, while anaerobes are organisms whose air requirement is low, seems 
to summarize most nearly the numerous contributions. 
The limiting effect of scanty aeration upon reproduction has already * 
been mentioned. Determination of the potency of this factor in any 
but general ways is difficult, because of other factors involved. 
Observation very early showed tha£ greater pycnidium production 
took place in a capsule or Petri dish than in a plugged test tube, and 
that small test tubes were not so effective for pycnidium production as 
larger ones. Similarly, when capsules were piled one on top of another 
in a battery jar, pycnidia production took place in the top capsules 
first, although in a few days or a week pycnidia were formed in all. 
