cf taxonomy is of 30 little value physiologically that most 

 students have long realized the great importance of giving 

 definite .information concerning trie previous history of their 

 experiment;;! organisms. 



(2) The nature of the medium, implying all the ph>c: 

 cal and chemical properties of the space about the hyphae , 

 their environment. If the fungus is partly in the air and 

 partly in a liquid cr gel medium this set of conditions re- 

 quires separation into two corresponding groups. For the 

 most part, the conditions of the medium (aside from tempera- 

 ture and radiation) involve the concentration of numerous 

 chemical substances such as oxygen, carbon dioxide, starches, 

 sugars, acids, inorganic salts, etc. 



(3) Temperatur e conditions . Since the temperature 

 of the hyphae follows closely that of the medium, and since 



the latter fellows the temperature of the more distant sur- 

 roundings of the culture, it is conventional to consider the 

 temperature of these surroundings as constituting a condition 

 in itself. After all, it is the temperature of the fungus 

 hypha that directly influences its rate of growth, not that 

 of the medium, culture dish or chamber about the dish, etc. 

 But since the temperature of these spaces are all practically 

 the same this last distinction has generally been ignored. 

 The temperature condition for two cultures may differ in sev- 

 eral ways. If they are maintained temperatures they m^y 



^fer in degree or intensity alone, and we may express them 

 in terms of degrees on some thermometer scale. If they are 



