

Since the amount of medium necessary for the entire 

 study cculd not well be made in a single day, about eir: " 

 liters were prepared at a time, until about 4fi liters were 

 ready. The entire amount *vas then liquified, placed in a 

 20 gallon earthen-ware vessel and thoroughly mixed, after 

 which it was poured into liter bottles. The mouths of the 

 bottles were then plugged with cotton in the usual way and 

 the bottled medium immediately subjected to a temperature of 

 115 C for 15 minutes. This heating was also repeated on the 

 two following days after which the tops of the cotton plugs 

 were flamed and covered with several thicknesses of paraffined 

 paper, tied tightly around the bottle neck. Tne bottles of 

 medium were stored in darkness at a temperature of about 18 0. 

 Wrei a lot of cultures were to be pads, the required number of 

 bottles of medium were removed from storage, brought into the 

 liquid condition by heating in the autoclave, and used ir 

 the ordinary way for pouring the plates. About 15 cc. of 

 medium was used: in each culture dish. It v/as found by test 

 that this amount might be increased or diminished by as much 

 as 3 cc. or more without perceptibly influencing the growth 

 of the funei. The bottoms of the dishes used had not been 

 planed, and slight irregularities in the glass produced cor- 

 responding differences i^- the thickness of the plate of medium. 



STOCK CULTURES 

 The original sources of the fungus materials were as 

 follows : -- Pythlacy s t ig ci trophthora isolated from the 

 diseased bark of a lemon tree suffering from 3ia, at 



25 



