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on various substrata, and of the production of sexual organs and 
oospores on a special oat medium. inton’s results are fully 
confirmed, and some new points, especially with regard to 
development of the spores, are brought to light. 
The medium on which antheridia and oogonia were induced to 
form was ground Quaker Oats agar. On this the fungus grows 
vigorously, and after producing a luxuriant crop of conidia develops 
oospores readily and freely. ‘The oospores arise as the result of the 
apparent fertilization of the oogonia by antheridia, their development 
following the process described by Pethybridge for P. erythroseptica. 
The spores measure 28—30y in diameter, and the wall is 2—4u thick. 
On Clinton’s oat-juice agar oospores were produced parthenogeneti- 
cally in the absence of antheridia, and the same phenomenon also 
took place to a large extent in the Quaker Oats cultures. In the 
case of the latter the authors believe that the formation of antheridia 
AL eG, 
* On Pure Cultures of Phytophthora infestans, De Bary, and the Development 
‘of Oospores. By G. H. Pethybridge and Paul A. Murphy, Sci. Proc. Roy. 
Dublin Soc., vol. xiii, No. 36, March 1913, pp. 566-588. 
