JEHANGIR FARDUNJI DASTUR 237 



been placed in the same basket and after inoculation they were all in the same 

 jar exposed to light. It is therefore difficult to understand why only two 

 of these cultures formed oospores while the remaining four developed only 

 sporangia and resting conidia. Subcultures were made on French bean 

 juice agar, Oat juice agar, Quaker-Oat agar and Wheat juice agar from these 

 cultures bearing oospores. Of these subcultures only one on Oat juice agar 

 developed oospores and although over a couple of dozen cultures were made 

 on Quaker-Oat agar from different sources still only one tube of this medium 

 gave oospores. Many cultures on Oat juice agar produced oospores but their 

 development had no relation to the parent cultures. Tubes inoculated with 

 cultures producing oospores did not necessarily bear the sexual organs while 

 transfers made from cultures on the same medium and from French bean juice 

 agar cultures not bearing oospores occasionally produced them. Thus it is 

 not easy to say what factor or factors stimulate the development of oospores. 

 This discontinuous production of oospores differs from the result got by 

 Pethybridge and Murphy^ with Ph. injestans (Mont.) de Barv, where 

 a culture once having commenced to form oospores, continues to do so 

 without break in the subsequent transfers. 



The development of oospores follows the method found almost simulta- 

 neously in five species of this genus, viz., Ph. erythroseptica Pethyb., Ph. 

 infestans (Mont.) de Bary, Ph. Phaseoli Thaxt., Ph. parasitica Dast. and Ph. 

 ColocasicB Rac. Anther idia and oogonia are always produced embedded 

 in the nutrient medium, and are as a rule borne on separate hyj^hse, but in a 

 few cases they have been found to be borne on a common stalk (Fig. 6). 



The antheridium of the Phytophthora upon Vinca is identical with that 

 of the castor parasite ; in certain cases branched and double antheridia 

 (Figs. 4 and 3) were observed in the fungus upon Vinca. 



Whenever it has been possible to trace clearly the oogonial stalk for some 

 distance it has been found that, like the antheridial stalk, it has a lateral origin 

 (Fig. 5). In a few cases the oogonium has been observed to be intercalar, so 

 also the antheridium. The oogonium has also been found to arise from within 

 the antheridium as in Ph. parasitica (Fig. 7). The tentative oogonial incept 

 is at first thin-walled and is distinguishable from the vegetative branches 

 of the hyphse by its having dense and coarsely granular protoplasm ; when 

 it comes in contact with an antheridium its apex as a rule swells before piercing 

 the antheridial wall. It generally enters the antheridium somewhere at or 

 near the base, as in the other species belonging to the " infestans-grou-p. " 



' Pethybridge, G. H., and Murphy, P. A. loc. cit. 



