36 Journal of Agricultural Research voi.xii, no. 



to get media on which the growth on each would be different for the same 

 organism. In other words, the media used were not intended to develop 

 general characters but specific ones which might differentiate the fungus 

 under investigation from other closely related species. 



NUMBER OF TUBES OF EACH MEDIUM INOCUL.^TED 



One tube of each of these 10 media was used in the series for any given 

 fungus. Better results would probably have been obtained by using 

 three or more tubes of each medium rather than one, but the writers could 

 not do this in their preliminary work for lack of sufficient equipment. 

 However, in a great majority of cases it is believed that accurate results 

 were obtained with these series of 10, since many of them have been 

 repeated to the fourth and fifth subcultures with different batches of 

 media, and the resulting characters when grown under the conditions 

 described below were practically identical for each subculture of the 

 fungus for each medium. 



POSITION OF CULTURE TUBES IN REFERENCE TO GRAVITY 



After inoculating the series of 10 tubes, they were placed in a horizon- 

 tal position, side by side, in shallow boxes with the surface of the agar 

 slant uppermost. The boxes were from 2 to 4 cm. deep and about 14 

 to 14.5 cm. wide. The culture tubes (150 mm. long or longer) had their 

 tops resting on the upper edges of the boxes and were therefore tilted at 

 a slight angle. These boxes were then placed on shelves in front of 

 windows with a western exposure where they received all of the diffused 

 light which came through and during the afternoon received the direct 

 rays of the sun from one to four hours daily. Under these conditions 

 the agar in the tubes gradually dried and the upper portion of it separated 

 from the glass, leaving a space of varying depth between the agar and the 

 glass, on which the aerial mycelium could grow even to the bottom of 

 the tube. 



AMOUNT OF DIRECT SUNLIGHT CULTURES RECEIVED 



The earlier cultures of the writers received only one or two hours of 

 direct sunlight. As the season advanced, the quantity of direct sunlight 

 received became greater, until finally the amount received was judged 

 to be too great and the intensity of the direct sunlight was decreased, 

 first, by a single screen of cheesecloth tacked over the front of the frames 

 holding the culture tubes. Later, a second piece of cheesecloth was 

 tacked over the first one. The general effect of the sunlight on the cul- 

 tures in the tubes thus exposed was to check the growth of the fungi, 

 compared to similar tubes when placed in very weak, diffused light or 

 absolute darkness. The sunlight also seems to intensify the colors of 

 the aerial mycelium when it is normally other than white. 



