TAXONOMIC CHARACTERS OF ALTERNARIA AND MACROSPORIUM 459 
of a lower temperature, cultures on standard bean agar were kept at 
10° C. The effect of acidity, also alkalinity, was determined on stand- 
ard bean agar, using 30 cc. and 20 cc. of normal hydrochloric acid, 
or 20 cc. of normal sodium carbonate per liter. A standard synthetic 
agar was used to study the effect of nutrition: 1.36 g. acid potassium 
phosphate, 1.06 g. sodium carbonate, .5 g. magnesium sulphate, 5 g. 
glucose, I g. asparagin, 15 g. agar, 1000 g. water. Variations from 
this standard were made by omitting glucose, doubling the amount 
of glucose, omitting asparagin, and by doubling the amount of as- 
paragin. Plain agar, 15 g. per liter of water, washed for several days 
in distilled water, was also used. 
Records of all cultures on the various media were made in tabular 
form, but for the sake of brevity only the table for cultures on bean 
agar is given here; the differences shown on other media being briefly 
summarized. Variations in size of spores are given on graphs one to 
nine. 
The most striking characters brought out by the colonies on the 
standard bean agar were the wide differences in the two strains of 
A. solani which on their hosts are indistinguishable. The strain from 
potato produced a pure white colony with marked red chromogenesis 
in the medium, had straight colorless submerged mycelium and no 
spores. On account of the abundant production of conidiophores and 
spores the strain of A. solani from Datura formed a gray colony, it 
produced no chromogenesis, and the submerged mycelium was dark 
olive and torulose. A. fasciculata, A. tenuis, and A. dianthi produced 
spores indistinguishable from each other. The conidiophores of 
A . dianthi were slightly larger in cross section than those of the other 
two. In general appearance of the colonies and in the production of 
aerial mycelium these three species were different. The other Alter- 
naria species studied were quite distinct in most cultural characters. 
The two species of Macrosporium were totally unlike except in general 
form of spores. 
Bean agar, 10°, jo days: Zonation was absent or inconspicuous in 
most of the colonies, especially in those of A, brassicae var. microspora 
which at 30° had the most marked zonation of all the species. This 
species also showed a marked alteration in color and form of its spores, 
these being light amber, nearly colorless, and about half the width of 
the normal dark olive spores. Another marked change occurred in the 
size and color of the spores of A . dianthi, these being twice their normal 
