260 
and cotton-boll Phytophthora with the exception that when a 
colony of a coconut culture was inoculated on a slant two days 
ahead of the cacao inoculation, the oospores which developed 
were on the average smaller than when the inoculations were 
made simultaneously. The data are summarised in the table 
‘showing the results for all cultures. 
The absence of oospores from pure cultures of the three 
Phytophthora, their close relationship as indicated by the mycelial 
growth and the size and shape of the asexual spores, and the 
more vigorous growth of the coconut and cotton boll strains 
which appear to be identical suggested rather strongly that all 
may be strains of one heterothallic species, the two vigorous 
forms being plus strains and the more weakly growing cacao form 
a minus strain. The behaviour of cultures grown from the 
oospores might be expected to throw further light on this 
hypothesis but unfortunately attempts to germinate them have 
not met with success, hitherto. The results moreover of growing 
the cacao and coconut forms in mixed cultures with strains of 
P. parasitica do not support that view. When the author was 
at Kew a mixed culture of the cacao Phytophthora isolated in 
Jamaica was grown on French bean agar with a strain of 
P. parasitica isolated from Ricinus communis in India by J. F. 
Dastur. The culture was maintained for two months in an 
incubator at 25° C. and then examined. Oospores were present 
in the cacao colony, averaging 23-6 » in diameter with a variation 
of 20-25-3y. Pure cultures of P. parasitica from castor develop 
oospores having a mean diameter of 18-6 yu. The form from 
budrot of the coconut was grown at the same time in mixed 
culture with a strain of P. parasitica from the coconut, which in 
pure culture developed oospores having a mean diameter of 
19-3 y. Oospores were numerous in the growth zone of the 
budrot form and in that of the “ parasitica ’’ strain but they were 
of the same size throughout the mean being 19-2. The fact 
that oospores of the same type and the same mean size and 
variation are formed in all mixed cultures of the cacao Phyto- 
phthora both with closely related forms and with an unrelated 
species indicate that the oospores are actually those of Phyto- 
phthora faberi. It is of interest to note that the oospores of the 
strain of P. parasitica developed in contact with the growth of 
the Phytophthora from coconut budrot were of the same size 
as those in pure culture. 
The oospores of P. faberi, which have normally a mean 
diameter of 23-1-23-6 and a variation of 17-8-28-6p, are 
substantially larger than those of P. parasitica (mean of 18-6) 
but approach closely in size to those of P. meadii, McRae (mean 
of 24-50) and P. colocasiae, Rac. It is evidently distinct from 
the last species. The coconut Phytophthora is apparently identical 
with P. palmivora, Butl. which should include provisionally the 
form which the writer obtained from cotton-bolls in St. Vincent. 
The absence of oospores both in pure and mixed cultures of this 
