258 
from the coconut and cotton-boll strains in growing less 
vigorously and in developing sporangia less luxuriantly but 
chlamydospores more freely; it does not form the characteristic 
mycelial aggregates usual in cultures of the coconut form. In 
all other respects including conidiophores and shape and size 
of the sporangia the three fungi cannot be distinguished in pure 
culture. Neither the coconut nor the cotton boll form has been 
found to infect cacao pods. 
The first observations on mixed cultures were made when 
the writer was working in the Mycological Laboratory of the 
Ministry of Agriculture at Kew (now the headquarters of the 
Imperial Bureau of Mycology) in the summer of 1920. Pure 
and mixed cultures of the cacao and coconut budrot Phyto- 
phthora isolated in Jamaica were grown on slants in tubes of 
French bean agar for two months (July-September) in an 
incubator at 25° ©. The two Phytophthora were inoculated 
in the mixed cultures by placing a fragment of agar carrying 
growing mycelium at two points on the slant about one inch 
apart. A colony of each form developed independently and 
after a few days they met and mingled. At the end of two 
months the pure cultures contained no oospores but they had 
developed freely in the mixed cultures throughout the colony 
of the cacao fungus and as far as the centre of the other growth. 
The mature sexual bodies were of the “infestans type” with 
persistant antheridia and a golden-yellow thickened oogonial 
wall. The mean size of 46 oospores was 23-3» and the extremes 
were 19 and 26-5 y; the oogonial wall averaged 29 u with a 
variation from 25 to 32-5 yw. The result of growing the two 
forms in mixed culture with strains of P. parasitica will be 
considered later. 
In order to confirm these findings, if possible, pure and mixed 
cultures of the cacao, coconut and cotton boll Phytophthora 
were grown in Barbados during the present year. The cacao 
culture was a recent isolation from a diseased pod in Grenada, 
the two cultures from the coconut had been isolated in Jamaica 
some years earlier while the cotton boll culture was a recent 
isolation from St. Vincent. |The Phytophthora were grown on 
slants in tubes from a single batch of lima-bean agar.* 
Five successive transfers of the pure cultures were made, after 
growth for two days, before mixed cultures were prepared in 
in a mortar and the pulp returned to the extract, the mixture 
t muslin and the latter squeezed. 16 grams of “ bacto” were 
added and the liquid boiled for a few minutes an ured through coarse 
muslin. It was tubed and sterilised in the autoclave at 12-15 pounds 
pressure for 20 minutes. This mode of preparation yielded a nearly cleat 
