320 Journal of Agricultural Research voi. xm. no. 6 



From ascospores. — Ascospores discharged on potato agar develop 

 a yellow color much like that described later for oat agar, but conidia are 

 produced early in greater abundance, and when these ooze out, the 

 culture becomes a dirty gray. Aerial mycelium is absent except on that 

 part of the culture which has begun to dry out.. 



CULTURES ON OATMEAL AGAR (SLANTED TUBES) 



From transfers of mycelium. — Cultures on oatmeal agar resemble 

 in form those on potato agar, except that the growth is not raised and 

 therefore the central knob is lacking. Growth is a little less vigorous. 

 Instead of a pink color, occasionally a yellow color is developed in a 

 portion of the culture, which becomes matted and wet as though bacteria 

 were present. This indicates the abundant development of conidia from 

 the mycelium without the formation of a definite acervulus. 



From ascospores. — Cultures from ascospores discharged on oat agar 

 are easily conspicuous by reason of the yellow color produced, which is 

 of much the same character as that produced on the living leaf. The 

 intensity of the color depends in part on the number of the fungus 

 colonies which are developed. If they are closely crowded, in the course 

 of two or three weeks the color is ochraceous orange. If the colonies 

 are less numerous, the color is duller, becoming a clay. Conidia are 

 produced more abundantly from the colonies with the larger amount 

 of surface space, being less crowded. 



CULTURES ON DEXTROSE AGAR (2 PER CENT DEXTROSE AND 2 PER CENT AGAR) 



From transfers of mycelium. — Growth is very meager. The larger 

 part of the mycelium is submerged in the substratum, and is dark olive 

 in color. Aerial mycelium is white. No conidia have been noted, even 

 after a growth of six weeks. 



CULTURES ON STERILE ALFALFA STEMS 



From ascospores. — The stem.s used for these cultures were gathered 

 standing through the snow in midwinter. When ascospores were dis- 

 charged on these stems, a growth resembling that on oat agar was pro- 

 duced. In two or three weeks the color on the more moist portions of the 

 stems was cinnamon-buff. On dry portions there was a little white 

 mycelium. Conidia are produced in great abundance. An illustration 

 of a way in which these conidia are occasionally borne on these stems has 

 already been given (fig. 3). The mycelium penetrates only a few outer 

 layers of cells of the substratum. 



Spore Germination 

 germination of conidia 



The first attempts to germinate conidia were made for the purpose of 

 isolating the fungus. But although plates were poured repeatedly, no 

 spore that could be identified as belonging to this fungus was ever ob- 

 sen/ed to germinate. 



