440 
JOHN A. ELLIOTT 
is incomplete and in some particulars inaccurate, but it is definite and 
complete enough to leave little doubt that what Nees described was 
what is now generally recognized as Alternaria. 
Fries (7) described the genus Macrosporium, differentiating it 
from Cladosporium, Helminthosporium, and Sporodesmium. The 
muriform spore, now given as one of the characters of the genus, is 
not mentioned in the generic description, otherwise it fits the present 
current conception fairly well. Having dropped the genus Alter- 
naria, Fries makes no mention of it in his description of Macrosporium. 
Macrosporium and Alternaria are placed by reason of their muri- 
form spores in the section Dictyosporae of the family Dimidiaceae of 
the order Moniliales, the muriform spores separating them from the 
genera Cladosporium and Helminthosporium, which in some species 
are in many particulars similar. Among the Dictyosporae there is 
little basis, as the genera are described, for separating Stemphylium, 
Septosporium, or Mystrosporium from Macrosporium. The separ- 
ation of the genera Alternaria and Macrosporium rests solely on the 
catenulation of spores in the former genus. The fact that many of 
the species of Alternaria now recognized were first described as Macro- 
sporiums indicates the uncertainty of this basis for generic distinction. 
In the specific descriptions in both genera, while mycelium, conidio- 
phores, and spores may all be taken into consideration, spore characters 
are the most used basis for distinction. 
The question of the validity of the separation of the two genera 
arose over the study of their ascigerous connection with Pleospora 
herbarum Tul. The Tulasne brothers (19) figure P. herharum bearing 
both Alternaria and sarcinaeform spores on the same hyphae. Gibelli 
and Grifhni (8), Mattirolo (13), Bauk (i), and Kohl (12), studying 
P. herharum in pure culture, concluded that it should be divided into 
two varieties or species, one having Alternaria conidia and the other 
having sarcinaeform conidia. Miyake (14), studying the life history 
of Macrosporium parasiticum Thum., found no Alternaria stage in the 
life cycle. Halsted (9), in studying the life history of Pleospora 
tropaeoli Hal. in pure culture, found that the cycle included only 
Pleospora and Alternaria stages. 
As the ascigerous stage of most species of Alternaria and Macro- 
sporium is unknown or non-existent, the basis for the distinction of 
genera and species must rest, in general, on the conidia. Jones (lo-i i), 
in studying Macrosporium solani E. & M. and M. fasciculatum C. & 
