450 
JOHN A. ELLIOTT 
sicae var. microspora (Berk.), Sacc, isolated from cabbage leaf spot 
(Brassica oleracea L.) ; A. fasciculata (C. & E.) J. & G., isolated from 
potato leaf spot; A. tenuis Nees, isolated from decaying wood; A. 
dianthi Stev. & Hall, isolated from Dianthus leaf spot; A. iridicola 
(E. & E.) n. com. {Macrosporium iridicolum E. & E.), isolated from 
iris leaf spot (7m germanica L.); A. sonchi Davis, isolated from leaf 
spot of Sonchus asper (L.) Hill; Macrosporium sarcinaeforme Cavara, 
isolated from clover leaf spot (Trifolium pratense L.) ; M. sarcinula 
Berk., isolated from decayed spot on Jonathan apple {Pyrus malus L.). 
All studies were made with pure cultures originating from a single 
spore of each species used, the spores being located on thin poured 
plates and transferred before germinating to other plates. The in- 
struments invented by Keitt^ greatly facilitated this operation. 
Whenever it was possible to do so, ten-day-old cultures were used 
as the standard for comparisons. Measurements of spores and conidi- 
ophores were made whenever present. In measuring spores a me- 
chanical stage was used and every spore on the slide which came within 
the field was measured for both length and width, thus eliminating 
unconscious selection. Curves of the measurements of each hundred 
spores were made for each culture. Since in a given species there is 
frequent variation in the length of the beaks, frorh one third to six or 
seven times the length of the spores, the beaks were not in any case 
included in the measurements. 
Graphs giving the superimposed curves of the measurements of 
one hundred spores of the same species under different conditions 
were prepared for the sake of easy comparison of the variations due to 
differences in cultural conditions (Graphs 1-9). 
Host Relation and Parasitism 
Inoculations were made on the natural hosts, on their near relatives, 
and on other plants, when there seemed to be any advantage in so 
doing. For example, Alternaria solani, which is morphologically 
similar to A. brassicae, was inoculated on cabbage leaves. 
The plants were inoculated by needle pricks and by placing spores 
in drops of water on the unbroken leaf surface. The percentage of 
successful inoculations was estimated from the needle pricks, since 
these were more easily located. An inoculation was considered suc- 
cessful if the fungus to a notable degree invaded and killed the tissues 
1 Phytopathology 5: 266, 191 5. 
