THE GENUS HYSTERIUM AND SOME OF ITS ALLIES. 629 
It will be observed that I have taken no note of the minor dif- 
ferences which the perithecia present. 
An examination of many varieties and specimens has shown 
that in H. pulicare, for instance, the perithecia may be long or 
short, wide or narrow, striate or smooth, with lips thin or thick 
and more or less gaping, the variations appearing to depend on 
the kind of wood, the age of the specimen, and the amount of 
heat, light and moisture to which it has been subject, and hence 
such characteristics are of little relative value. 
t is supposed that besides the ascous form, Hysterium has 
other modes of manifestation ; for instance, Tulasne affirms that 
Leptostroma vulgare is a form of Hysterium herbarum; the argu- 
ment being the usual one of post hoc ergo propter hoc, that is, 
Hysterium herbarum has been found either coincident with, or im- 
mediately succeeding to the Leptostroma on the same matrix. As 
I have elsewhere insisted, the only way to settle me de coreg is 
by culture of the various forms upon different matri 
The germination of Hysterium spores goes on on well in an 
ordinary growing slide, and the results are very interesting, es- 
pecially in regard to those species with cellular spores, in which 
each loculus gives rise to a mycelial filament. I have several 
times observed a connection formed between neighboring filaments, 
resembling very much the sexual process as it occurs in some 
algæ, but as yet am not prepared to say that it is of a sexual na- 
ture. I recommend the subject for observation and experiment 
to those who have microscopes and no definite work on hand for 
their instruments. 
The best classification of the Hysteriacei is that of M. Duby, 
but I think he has been premature in his effort to construct half a 
dozen new genera. The old division of Lophium, Glonium, Acti- 
dium and Hysterium serves well enough for identifying purposes, 
although as stated in the commencement of this paper, those 
forms of Hysterium, with thin membranous perithecia found in 
leaves and herbaceous stems, may be Conveniently referred to the 
subgenus Hypoderm 
The data are a Fairs for a revision of this family with a 
view to indicating their relations to other fungi and to each other. 
The accompanying plate gives the figures of the spores of the 
common forms of Hysteriacei magnified five hundred diameters. 
Fig. l represents a very large spore from a specimen in Mr. Rav- 
