14 



to such agar increased the tbiekuess of tbe stroma. The stroma was 

 better developed than in the same agar with only 0.2 per cent sugar. 

 In agar with 12 per cent cane sugar there was a great increase of this 

 tissue, which formed a sort of monstrous stromatic mountain the whole 

 length of the long slant. This ridge was 1 centimeter wide and fully 

 one-half centimeter high in its highest parts. Its very irregular, tough, 

 gray- white surface was covered with a thin layer of white aerial hyplne, 

 and 24 days from sowing was thickly set with colorless perithecia. 

 The latter were, however, also visible at this time on the scanty, 

 non-stromatic mycelium which had climbed up on the walls of the tube 

 above the agar. The formation of perithecia in a similar way was also 

 observed in other culture media. So far, therefore, as this fungus 

 affords any basis for judgment, the stroma is one of the most easily 

 variable parts of a fungus; consequently it appears hazardous to make 

 separation of closely related forms into distinct species solely on the 

 presence or absence of a stroma. 



(2) The color of the mycelium,— The variability in color according to 

 the nature of the substratum has been a subject of much interest to the 

 writer. In the interior of the host plants the fungus is usually pure 

 white, except in cotton, where the older mycelium is frequently brown. 

 For a considerable time the writer supposed pure white was its only 

 color, but trial of a variety of culture media brought to light some very 

 unexpected and most astonishing facts. 



The melon fungus is pure white on slightly alkaline nutrient agar. 

 The fungus remained snow white for over a month on alkaline corn 

 starch steamed in distilled water with asparagin added. In another 

 series it was pure white for 11 days, but had become faint rose color on 

 the fourteenth day and remained so up to the twenty-fifth day. 



On boiled rice, with the addition of bicarbonate of soda, the fungus 

 remained pure white for 40 days. 



On crushed cowpeas, steamed in distilled water, tht^^ fungus made a 

 copious growth from the start, but remained snow white as long as the 

 cultures were under observation (10, 17, and 22 days). 



The fungus was pure white in slightly alkaline, peptonized beef broth, 

 and did not become colored on addition of cane sugar or of dextrin. 



On acid, neutral, and alkaline nutrient gelatin the fungus madea pure 

 white growth. 



In acid potato broth the fungus was white for 11 days, except for 

 certain hyphal strands which had climbed out of the fluid and were 

 attached to the walls of the tubes. The submerged growth and the 

 pellicle were pure white. The following acids were tried with this broth : 

 Malic, oxalic, succinic, tartaric, and citric, 1 c. c. of the -i^ normal solu- 

 tion being added in each case to 10 c. c. of the broth. The behavior of 

 the fungus was the same in each case, white on and in the fluid, with 

 brown hyphte on the walls above it. 



On strongly alkaline litmus agar the fungus was white on the sixth 



