

physiological processes of any organism, may be expected 

 from biological tests in which any of the effective condi- 

 tions are allowed either to vary or to differ in unknown 

 ways. A3 long as the conditions differ only in known v/ays 

 from one culture to another, or as long as they vary only 

 in known ways in the same culture, there is hope of advanc- 

 ing our knowledge of environmental influences. The present 

 study was planned so as to approach as far as possible the 

 fulfillment of these general needs, as will be brought out 

 in the next succeeding paragraphs. 



In order that each fungus should always have approx- 

 imately the same internal characteristic at the beginning 

 of all the experimental cultures, the four species were kept 

 in stock tube cultures with ordinary corn-meal agar, and at 

 a temperature of about 16-18° C. From these primary stock 

 cultures inoculations were made, at frequent intervals, on 

 agar plates kept at a temperature of about 18° C. These 

 formed the secondary stock cultures. The marginal region 

 of the mycelial disk of a secondary 3tock culture (about 5 

 days from inoculation) furnished material for inoculating 

 the experimental cultures of that fungus. From various 

 lines of evidence (especially that of experiments repeated 

 after long intervals) it may safely be stated that the in- 

 oculation material for any one of the four fungi was always 

 practically the same, as to internal characters (tone, vigor, 

 etc. ) when the experimental cultures were started. Practi- 

 cally the 3ame amount of inoculation material was always 



12 



