REPORT OF THE SOCIETY 



131 



Spore suspension was adopted. A stock culture, on potato-dextrose agar, of 

 the organism to be used (which was well covered with spores) was thoroughly- 

 stirred in sterile water in the tube in which it was growing. The stirring was 

 done with a sterile glass rod. The suspension was then poured on a screen of 

 fine-meshed muslin in a funnel, and strained into a sterilized flask. This gave 

 a liquid turbid with spores, most of which had been shaken apart and floated 

 free in the liquid. Very little other material passed into the flask. For inocula- 

 tion one cc. of this liquid was passed into each flask by means of a sterile 

 pipette. This gave an abundance of spores, which were uniformly distributed 

 in the culture media. 



The cultures were allowed to grow for a period of sixteen days in an incu- 

 bation chamber where the temperature did not vary more than two degrees. 

 The chamber was lighted with electric lights all the time during the period of 

 growth. The yield of dry material produced was used as an indication of the 

 effect of the food supplied. The dry weight of material was obtained by fil- 

 tering through a filter paper which had previously been weighed. The filter 

 paper containing the mycelium was then placed in a drying oven kept at a 

 constant temperature and left there until thoroughly dried. The filter papers 

 were again weighed and the amount of dry weight calculated. All the yields of 

 each series were subjected to the same conditions in drying. 



The H-ion concentration of each culture solution was determined before 

 the flasks were inoculated and after the period of growth. The colorimetric me- 

 thod of H-ion determination as described by Clarke and Lubs ('17) and later 

 more fully by Clarke ('21) was used in this phase of the work. From time to 

 time the electrometric method was used to act as a check. 



The results of the cultures of the Quebec organism, are given in the following 

 table. The results obtained from the other fiv^e organisms were very similar 

 to this : 



Note: These results are the average of two sets of culiures. 



