354 BOTANICAL GAZETTE [November 



Atkinson, to whom I wish to express my thanks for his advice 

 and kindly criticisms. 



Material and methods 



A single plant of this species was discovered growing on an 

 aphid which had accidentally fallen into one of several water cul- 

 tures prepared for the purpose of entrapping various Phycomycetes. 

 The specific culture referred to was made from soil and decaying 

 vegetation taken from the bottom of a small almost dry inland 

 pond in the vicinity of Ithaca. When first observed the plant bore 

 large numbers of resting sporangia, whose arrangement and bright 

 orange color gave it a very beautiful appearance. After washing 

 through several changes of sterile water, the plant was placed in a 

 solid watch glass for further observation. On examination the 

 following day it was found that a number of zoosporangia had 

 developed, a few of which had already discharged the characteristic 

 zoospores first described by Thaxter (9) for B. Pringsheimii. 



Cultures were immediately started with aphids and other 

 animal tissue, from which an abundance of material in all stages of 

 development was secured. After making several unsuccessful 

 attempts, a pure culture of the organism was obtained in the follow- 

 ing manner: A few nearly mature zoosporangia were cut from a 

 plant, carefully washed until practically free from contamination 

 and allowed to discharge their zoospores in sterile water. By 

 means of a platinum loop the water containing the zoospores was 

 spread over the surface of newly prepared slants of sweet corn agar. 

 In a few days the small plants appeared as more or less isolated 

 refractive specks on the surface of the agar, and were easily lifted 

 out with a sterile needle and transferred to new tubes. 



Material for sectioning was obtained in various stages of 

 development from both water and agar cultures. It was soon found 

 that the latter yielded just as good and more easily handled material 

 than the former and it was therefore more frequently used. To 

 secure the best results with the latter method, plants bearing nearly 

 mature zoosporangia were transferred to the middle of a poured 

 plate of either potato or sweet corn agar, preferably the latter, in a 

 few drops of sterile water. After a few hours to one day large 

 numbers of zoospores will have been discharged and can easily be 



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