taxonomic characters of alternaria and macrosporium 469 
Host Relation 
Inoculations upon host plants show that some species are quite 
narrow in their range; e. g., A. sonchi was parasitic on Sonchus asper 
and Lactuca canadensis but failed to maintain itself on cultivated 
lettuce and other Compositae. Others may be broader in their range, 
growing actively on many species of one family and less actively on 
other families; as, A. solani which grew actively on all solanaceous 
hosts used and less actively on cabbage. A. hrassicae var. microspora 
grew actively on all cruciferous hosts inoculated but failed in all inocu- 
lations outside of that family. Forms morphologically inseparable 
may grow on different hosts and fail to cross-inoculate, or of several 
forms morphologically alike only one strain may be parasitic. On the 
other hand, forms which are morphologically clearly distinct may be 
equally parasitic on the same host. 
The studies here presented would seem to show that the present 
tendency toward limiting the distinction of species to differences in 
morphology, regardless of host relationships, is commendable. They 
would seem to indicate, further, that characters should be sought which 
are least affected by cultural conditions, and in using such characters 
due consideration should be taken of factors liable to make those 
characters variable; such as, age or stages in development. 
VI. GENERIC LIMITATIONS OF ALTERNARIA AND MACROSPORIUM 
A. ALTERNARIA 
In every case where species of Alternaria have been described, the 
spores have been more or less elongated and pointed at one end. In 
the present studies all spores of the obclavate, cuneate, or ovate form 
produced chains of spores under favorable conditions. Since the 
species studied in culture covered all the types of spores found in 
exsiccati or described in the ''Sylloge Fungorum" under the genera 
Alternaria and Macrosporium, there is no doubt that all of the species 
with these types of spores belong to the genus Alternaria, that most of 
the species named under Macrosporium belong to this genus, and 
can be recognized as such by the descriptions given of their spores. 
The term "clavate," as applied to the Alternaria spores, is a 
misnomer arising from a misconception and carrying misconception 
with it. Without exception the pointed end of the spore is the apex 
and the rounded end is the base. Alternaria tenuis has been figured 
with its spores attached by their apices, and as this error was widely 
