114 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 6 



they were transferred to sterile Douglas fir and hemlock saw- 

 dust in Erlenmeyer flasks for keeping. All three forms grew 

 comparatively well on both kinds of sawdust. 



Optimum degree of acidity of media for fungi used. — In con- 

 nection with this work it was necessary to determine whether 

 or not slight changes in the reaction of the medium had any 

 influence on the rate of growth of the fungi. Media of differ- 

 ent degrees of acidity were therefore made up. Three liters 



of medium having the following composition per liter were 

 prepared : 



Extract from 450 gms. carrot 



Glucose 10 gms. 



Agar 25 gms. 



Distilled water to make . . 1000 cc. 



Two-hundred-cc. amounts of this medium were placed in 

 500-cc. Erlenmeyer flasks and autoclaved for twenty minutes 

 at fifteen pounds. This medium titrated +13.5 Fuller's scale 

 after autoclaving. After adding varying amounts of sterilized 

 hydrochloric acid or sodium hydroxide to the flasks samples 

 were again titrated while the agar was still in a liquid condi- 

 tion. Twenty-cc. amounts were placed in each of six Petri 

 dishes of approximately nine centimeters diameter. Before 

 inoculating these plates with the fungi they were allowed to 

 stand for three days at room temperature in order to deter- 

 mine whether or not they were sterile. For each fungus two 

 plates were used for each concentration. The colonies were 

 measured in two directions at right angles to each other and 

 the average taken. 



It was endeavored to inoculate all plates in a practically 

 identical manner, and to do this, plate cultures of the fungus 

 in question were cut by means of a sterile scalpel into squares 

 measuring approximately three-quarters of a centimeter on 

 each side. A single square was placed in the center of each 

 plate and after. six and again after eight days' incubation at 

 room temperature the size of the colonies was measured. The 

 results are tabulated in table xin : 



