TAXONOMIC CHARACTERS OF ALTERNARIA AND MACROSPORIUM 473 
The A. sonchi group. A. sonchi Davis is different from any of the 
species in the above groups in having large-celled spores with a mark- 
edly obtuse apex (fig. 5, spores of the A. sonchi group). The range in 
size is 50-125 X 12-25 M- No similar form was found in exsiccati. 
1 2 
/00/M. fOO/^ too/^ 
4 
6 
5 
Text-figs. 1-6. — For explanation see text. 
The A. hrassicae var. microspora group. The spores of ^. hrassicae 
var. microspora (Berk.) Sacc, differ from those of A. tenuis in being 
uniformly narrower and less muriform ; longitudinal septa seldom being 
formed (fig. 6, spores of the A. hrassicae var. microspora group). Here 
belong those of group 7, page 447. 
A more complete study of exsiccati might show the necessity of 
other groups for forms not included above. 
Without doubt the number of valid species of Alternaria is a very 
small percentage of the present named species of Alternaria and Ma- 
crosporium, but it is outside of the limits of the present paper to reduce 
these names to synonymy. 
VIII. SUMMARY. 
1. Spore shape in the genus Alternaria is correlated with catenula- 
tion of spores. 
2. All obclavate, ovate, cuneate, or elongate-pointed spores of the 
Macrosporium-Alternaria type form chains and belong to Alternaria. 
3. The acute end of the spore is the apex or beak, not the base or 
pedicel. 
