TAXONOMIC CHARACTERS OF ALTERNARIA AND MACROSPORIUM 46 1 
dimensions and of much lighter color (Plate XIX, 10). A marked 
change in the character of both the aerial and submerged mycelium 
occurred in M. sarcinaeforme, which is normally black, but here was 
white. All colonies were much retarded in rate of growth, the amount 
varying with the species. Five produced no spores. 
Bean agar + jo Fuller's scale, jo°, 10 days: This medium did not 
solidify and in many cases the whole colony was saturated with it. 
There was little variation in the general appearance of most of the 
colonies from that on standard bean agar. Two variations worthy of 
note were the absence of zonation in colonies of A. brassicae var. 
microspora, and the more than usual production of aerial mycelium on 
colonies of A. brassicae var. nigrescens. The chromogenesis of A. 
solani from potato was more marked on this than on any other medium. 
Some species which usually produced spores in more or less abundance 
produced few spores or none on this medium. They were A. brassicae 
var. nigrescens, M. sarcinaeforme and M. sarcinula. The spores of 
A. sonchi and M. sarcinula were below normal size. 
Bean agar + 20 Fuller's scale, jo°, 10 days: Except for a little 
greater production of aerial mycelium by most species, the general 
appearance of the colonies was like those on neutral bean agar. Chro- 
mogenesis of A. solani was very marked, also the submerged mycelium 
of this species was darker than normal. A. brassicae var. nigrescens, 
M. sarcinaeforme, and M. sarcinula produced fewer spores than on 
neutral agar. 
Bean agar — 20 Fuller s scale, jo°, 10 days: On the alkaline bean 
agar the most notable feature was the abundant production of spores 
by A. brassicae var. nigrescens, which ordinarily produced few spores 
on artificial media or on its natural host. In this instance the spores 
covered all parts of the colony. A. solani from potato, which on 
neutral and acid media produced marked chromogenesis, on the al- 
kaline medium produced none, and the submerged mycelium, in the 
older part of the colonies, became dark. A. dianlhi and M. sarcinula 
produced spores smaller than normal on the alkaline medium. The 
general appearance of the colonies was little different from that on 
neutral bean agar with the exceptions already noted. 
Standard synthetic medium, jo°, 10 days: Except for a general lack 
of aerial mycelium and the appearance of less luxuriance, the colonies 
were little different from those on the standard lima bean agar. 
Standard synthetic agar minus glucose, jo°, 10 days: The appearance 
