234 PHTTOPHTHOEA ON VINCA ROSEA 



Similarly sterilized follicles were placed in water in watch glasses, and were 

 kept in moist chambers under aseptic conditions. These follicles wore 

 inoculated by zoospores from the same culture. Those in the tubes did not 

 take the inoculation, even though in many cases aerial mycelium was found 

 growing from the bits of agar medium used for inoculating the follicles ; 

 while those left in water showed signs of successful inoculations in 

 twenty-four hours by the rotting that had set in ; an aerial growth of 

 mycelium soon followed. These inoculation experinxents sufficiently 

 show the weak parasitism of the fungus on Vinca rosea. Perhaps this is the 

 only strain as yet isolated from any species of Phyfophfhora having such a 

 weak parasitism. 



On diseased leaves, sporangia were formed on both the surfaces, borne 

 on short or long sporangiophores (from 3-4 to over 375^ in length) and emerging 

 as a rule singly through stomata ; in rare cases, sporangiophores have been 

 found to be branched ; two or three emerging together from a single stoma 

 have also been observed. The sporangiophore, in a few cases, has been found 

 to make its way out by rupturing a guard cell. Sporangia are sometimes borne 

 on such short stalks that they almost seem to be sessile. From petioles and 

 stems sporangiophores emerge singly or in clusters through any part of the 

 epidermis as in Ph. ijarcmtka Dast.^ Sporangia are generally pear- 

 shaped, but often irregular ones have been found. The mycelium within 

 the tissues is both inter and intra-cellular. Haustoria have not been 

 observed. 



This Phylophthora was easily taken iu pure culture. Diseased leaves 

 and follicles, washed with corrosive sublimate (1 in 1,000) for five minutes 

 and then with sterilized water, were incubated and gave, after a few days, 

 a woolly growth. From this pure cultures were obtained by inoculating tubes 

 of Quaker-Oat agar ; this medium was prepared as recommended by 

 Pethybridgo and Murphy. ^ Also seeds removed aseptically from diseased 

 follicles similarly sterilized on the surface, were introduced in tubes containing 

 nutrient agar and subsequently gave pure cultures of the fungus. 



The growth of this fungus on artificial media is very similar to that of 

 Ph. parasitica^ on castor, and also the vegetative, asexual and sexual 

 reproductive organs ; therefore a detailed description is not needed. 



) Dastur, J. F-, on Phytophthoni parasUica nov. spec. i/ew. /)cp<. Aijric. India, B<>l. 

 Her., V, No. 4, 1913. 



2 Pethybiidgc, G. H. and Murpliy, V. k., On Pure Cultures of Ph. uife4ans dv Bury, 

 and the Development of Oospores. 6'c. Proc. Roy. Dub. Soc, XIII (N.iS.), No. 36, 1913. 



