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the way described above. Each combination was run in duplicate 
by reversing the position of the two colonies on the slant. The 
cultures stood on a table under a large bell jar in subdued light 
from the middle of April to the middle of July when they were 
examined. The temperature of the room seldom exceeded 30° C. 
and was never below 22° the mean being near 26°C. No oospores 
could be found in any of the pure cultures and they were not 
present in the mixtures of the two coconut cultures nor in the 
mixtures of those with the cotton-boll culture. Oospores were 
present, however, in all the mixed cultures containing the cacao 
Phytophthora. In these mixtures of the cacao fungus with the 
two coconut cultures and the cotton boll culture the sexual spores 
were of the “‘ infestans type’’ witha yellow more or less thickened 
oogonial wall. The thick-walled hyaline oospore filled the 
oogonial cavity, as a rule, leaving only a dark line between the 
walls, but examples were frequent in which the oospore did not 
fill the cavity. A persistant antheridium was always present, 
usually hyaline but occasionally stained yellow. The oogonia 
and antheridia always appeared to be developed on separate 
hyphae but it was not possible to trace these hyphae definitely 
to the same mycelium. The interesting observation was made 
that in a few examples no walled oospore was present but the 
plasmatic contents completely filled the mature thick-walled 
yellow oogonium, the wall of which showed the pitted appearance 
characteristic of the mature chlamydospore; in all such cases 
a perfect persistent antheridium was present. The oospores 
were developed in the dense surface plectenchyma, and to a 
depth of about 2 millimetres below it: they were scanty at 
greater depths in the agar. In some portion of the slants, the 
mature oogonial wall showed a dark, rather indefinitely limited 
outer zone with a rough or wrinkled surface but elsewhere this 
zone was lacking and the wall appeared to be smooth. Oospores 
were abundant throughout the growth area of the cacao Phyto- 
phthora but became scanty towards the centre of the other colony. 
There was mutual penetration of the two colonies but the vigorous 
coconut and cotton-boll strains appeared to push into the colony 
of the cacao fungus deeper than the latter did into their zones. 
This tendency was clearly shown in some additional mixed 
cultures in which a colony of the coconut Phytophthora was 
allowed to develop for two days before the cacao fungus was 
inoculated on the upper part of the slant. In these examples, 
oospores were present up to the apex of the slant and the mycelial 
aggregates of the coconut strain were present at the apex also, 
indicating that it had grown through the cacao colony. A series 
of transfers of the pure cultures at short intervals did not appear 
to be necessary for subsequent development of oospores in the 
mixed cultures as they were formed abundantly when the 
cultures were mixed after one such transfer. 
The mean size and variation of the oospores were approxi- 
mately the same in all combinations of the cacao with the coconut 
A2 
