Jan. IS, 1920 Further Studies of Sorosporella uvella 423 



agar was the first nutrient to be used, and it was subsequently dis- 

 carded as unsuitable. Its use for the first cultures led almost to failure, 

 for some of the plates were discarded after a period of 10 days, when there 

 appeared to be no growth. Fortunately other plates were retained for a 

 longer period; and after 2 weeks a few mycelial strands were obsen-ed 

 which could be traced to the spore aggregations, but impurities crept in 

 and crowded out the slow-growing Sorosporella. After numerous fruitless 

 attempts, however, pure cultures were obtained on other more suitable 

 media, from which subcultures have since been made without difficulty. 



Fawcett (7), in cultivating the entomogenous Aschersonias of the white 

 fly in Florida, met with the same difficulty ; he found that such fungi grew 

 very slowly on artificial nutrients. In fact, he attributes failure in the 

 past in cultivating the species of Aschersonia to the fact that plates were 

 discarded before the organisms had time to develop. 



Although a number of media have been employed, several of which 

 are suitable, the writer now uses Molisch's culture media for luminous 

 bacteria*, modified to some extent, because it is readily made and seems 

 well suited for Sorosporella. This nutrient will hereafter be called 

 Molisch's agar or Molisch's solution. 



After the fact was established that the fungus under consideration 

 could be successfully cultivated artificially, a variety of nutrients were 

 employed, on several of which its development was found to differ some- 

 what from that which occurs in infected insects. Furthermore, single 

 conidia and single resting spores were isolated by Barber's pipette holder 

 and placed in a nutrient drop of agar in a Van Tiegham cell, where de- 

 velopment from day to day was easily noted; and pure cultures were 

 subjected to different environmental conditions in order to determine 

 the optimum temperature for growth of the organism as well as its 

 behavior in unusual atmospheres. 



To determine the optimum temperature a number of tube cultures 

 were inoculated at approximately the same time. A few were placed in 

 an incubator, a few in a water cooler, and others were kept in the labora- 

 tory. The temperature of the incubator varied from 35 ° to 40° C. , that of 

 the water cooler from 18° to 20°, whereas that of the room ranged from 

 22° to 35° during the month that the tests were in progress. In the 

 incubator the fungus developed feebly though in a normal manner, the 

 thallus covering an area no greater than a square centimeter one month 

 after inoculation. In the water cooler, on the contrary, gro\\i;h was very 

 luxuriant; and within the same space of time the fungus had spread over 

 the entire surface of the agar slants. The room temperature for the 

 first week or so was quite high, varying between 32° and 34°, and gro\\i:h 

 of the organism did not keep pace with that in the cultures in the cooler ; 

 but later when the room temperature dropped the fungus began to 



'Water, 1,000 cc; agar, 15 gr.; sugar, 20 gr.; peptone, 10 gr.; dipotassium phosphate, 0.250 gr.; mag- 

 nesium sulphate, 0.250 gr. 



