84 



ditions of moisture, in air and medium, that it is far from being a reliable 

 character for separating the two. 



Green-wheat agar. (Formula as for corn-meal agar, substituting for the 

 corn-meal live wheat leaves and stems which had been_ passed through 

 a meat-grinder.) H. No. 1 grew well, producing a dense colony, but with 

 weak zonation and with much woolly, white aerial mycelium, and but few 

 and scattered conidia. This medium, while apparently very nutritious, 

 favored abundant vegetation rather than sporulation, and was a poor 

 medium for the differentiation of races. 



To determine the effect of reducing the nutrients in green-wheat 

 agar, this was combined, in varying proportions, with washed agar with 

 varying results. On washed agar the growth of H. No. 1 was scant, color- 

 less, and with no conidia, the colony diameter reaching only 5.5 cm. in 

 9 days. As the content of green wheat was increased, there was a gradual 

 increase in density of colony and of aerial mycelium. In 9 days the colony 

 diameters were as follows: 



On 25% green- wheat agar. .9 cm. 

 On 50% green-wheat agar. .8 cm. 

 On 75% green-wheat agar. .7.5 cm. 

 On 100% green-wheat agar. .7.5 cm. 



These colonies showed no dark color and only very weak zonation, 

 and in the two high concentrations the aerial mycelium developed into a 

 dense, closely felted mat. Conidia were produced scantily and varied 

 greatly from the shape found elsewhere, being less tapering, more nearly 

 cylindrical, and materially thicker (Graphs 13, 14, Fig. D). In some 

 instances septation differed markedly diminished (Graphs 15, 16, Fig. D). 

 Many large conidia had no septa at all, and others had irregular or incom- 

 plete septa. It is evident that this medium, even at 25% strength, in- 

 duces many abnormalities, and the very high coefficient of variability 

 is especially striking. The differences in septation here noted were not 

 constant on the same plate and were much more common at the drying 

 edge. On this agar conidial length was less than under standard conditions 

 (see appendix, p. 180). 



Wheat-straw agar. (Fifty grams of old wheat-straw, boiled 20 minutes 

 and filtered.) Growth was poor. 



"Difco" beef -agar. H. No. 1 grew slowly but was very dense; surface 

 even; little aerial mycelium. 



