SUMMARY. 



1. A weak parasite belonging to the genus Phytophthora was found 

 attacking Vinca rosea in May, 1913, under very wet climatic conditions. 



2. Microscopic characters of this disease in Vittca are similar to those of 

 Ph. 'parasitica Dast, on castor except that sporangia are borne on both the 

 surfaces and that sporangiophores are smaller, 



3. Asexual spores agree with those of Ph. jtarasitica ; the chief 

 differences are that resting conidia are smaller and zoospores produce as 

 many as four germ-tubes while those of Ph. parasitica have not been 

 observed to produce more than two. 



4. The formation of oospores is identical with that of Ph. parasitica. 

 The size of the oospore like that of the oogonium is influenced by the medium 

 in which it grows. On certain media (Oat juice agar and Quaker-Oat agar) 

 the measurements agree closely with those of Ph. parasitica from castor. From 

 the few cases of the germination that have been observed it appears that the 

 mode of gernaination is the same as that observed by Pethybridge in 

 Ph. erythroseptica Pethyb. 



5. Inoculation experiments show that there are some points of difference 

 between the Phytophthora on castor and that on Vitica. Tlie latter 

 is distinctly weaker in parasitism than the former. Some of the liosts are 

 common to both, while some which were attacked ])y the Vinca parasite 

 resisted infection by that from castor. 



6. It is concluded that the fungus is not a distinct species but only a 

 biologic strain of Ph. parasitica Dast. 



