Aug. ii, 1923 
Phytophthora Faberi on Coconut and Cacao 
273 
merits of the diameter of the mycelial mass in each case. Very slight 
growth for both strains was noted at 12 0 . The vegetation gradually in¬ 
creased in extent up to between 27 0 and 30°. From 30° and above there 
was a gradual decrease. The optimum growth occurred between 27 0 and 
30°, being nearer 27 0 . Growth still was very good at a temperature 
of 32°. Below 12 0 no growth was noted. Neither fungus strain, how¬ 
ever, was killed when held at an average temperature of 11.5 0 for 16 
days, for growth took place after removal from the incubator. When 
kept at an average temperature of 7.5 0 , the minimum being about 6° 
for the same period, they were killed. 
In all cases of growth the hyphae grew into the agar. At the lower 
temperatures the mycelium formed a dense, flat, surface mat with few 
aerial hyphae. At temperatures of 22 0 , and above, a tufted, serial mass 
of hyphae was produced, radiating out from the center. No spores were 
formed at the lower temperatures, between 12 0 and 20°. Few conidia and 
chlamydospores developed at the higher temperatures on the plates kept 
in the dark. In cases where spores formed in the dark, the .chlamy¬ 
dospores appeared to predominate. There was a marked contrast be¬ 
tween the growth on plates of both strains of the fungus kept in the light 
at a room temperature of about 22 0 and that on plates kept in the dark in 
the incubator at the same temperature. In both cases the vegetative 
development was approximately the same in extent. In the dark, how¬ 
ever, the granular development of aerial hyphae was not produced and 
few conidia and chlamydospores formed. The growth on plates in the 
light was tufted, aerial, and granular, with an abundance of both chlamy¬ 
dospores and conidia. The development of the coconut strain is clearly 
shown in Plate 7, A. 
Another check on the optimum temperature growth for both strains 
was obtained in temperature experiments on zoospore production. A 
suspension of spores from corn meal cultures was made in distilled and 
tap water. Vials containing 5 cc. of these suspensions were placed at 
temperatures in the Altmann incubators ranging from 7 0 to 32 0 and at 
room temperature exposed to the light. In no cases during these trials 
were zoospores produced, but an abundance of direct germination devel¬ 
oped. The trials were run for one and three days, respectively. Very 
slight direct germination of the spores from either strain was noted at a 
temperature of 7 0 . Germination and growth then increased with the 
increase in temperature, being best between 20° and 27.5 0 . The opti¬ 
mum temperature for direct germination and growth appeared to be 
around 27.5 0 . At 30° germination and growth were not so good. The 
effect of light and dark at room temperatures showed no difference in 
the germination. 
RELATION TO ACIDITY AND ALKALINITY 
The relation of both organisms to acidity and alkalinity was deter¬ 
mined by growing them on plates of potato dextrose agar and in Czapeks 
solution at various hydrogen-ion concentrations ranging from 1.4 to 10+ 
for the potato dextrose agar and from 2 to 10+ for the Czapeks solution. 
During the period of the experiments the room temperatures ranged 
between 21.5 0 to 27.5 0 , with an average temperature of approximately 
23°. In both cases the vegetative growth was determined by measuring 
the diameter of the growth at the various concentrations. In all cases 
