240 



PUYTOPUTHORA ON VINCA ROSEA 



from the few oospores of the PhylofhtJiora on Vinca rosea, that have been 

 observed germinating, it appears that the mode of geimination agrees, at 

 least in essential points, with that of Ph. erythroseptica described minutely 

 by Pethybridge. 



On account of the peculiar mode of development of oospores, this fungus 

 belongs to what Pethybridge^ calls the " wfestans-giou])" Of all the species 

 of this group, the Phytophthora on Vinca rosea is most clcsely allied 

 to Ph. parasitica Dast. on castor. Inoculation experiments were carried 

 out to trace further the affinity between these two. From the very 

 commencement of the study of this parasite it was found that, in order 

 to get successful results, the inoculated plant, even if it be the original 

 host, must be kept in an atmosphere saturated with moisture. Inoculated 

 plants were, therefore, always kept in such an atmosphere as described on 

 page 233. It may be noted that no such precautions were required with j)lants 

 successfully inoculated by Ph. parasitica, and that the negative results of the 

 inoculation of certain plants detailed below with the Phytophthora on castor 

 have been obtained even when they had been tried under very moist 

 conditions. Inoculations on living plants were in all cases made by means 

 of zoospores from pure cultures. 



The following table shows the results of various inoculation experi- 

 ments : — 



1 Pethybridge, G. H. On the Rotting of Potato Tubers by a Now Species of Phytophthora 

 having a Method of Sexual Reproduction hitherto undescribcd. Sc. Proc. Roy. Dub. Soc, 

 XIII ("n. S.), No. 35, 191:5. 



