— 100 — 
was still less at home in Trichostomum. It has with us sometimes been confused 
with Gymnostomum or Hymenostylium. Holzinger's h under No. 2g of his ex- 
siccati is, for example, this species and not Gymnostomum curvirostrum scabrum 
as labeled. Kindberg's Gymnostomum platyphyllum {Hymenostylium platy- 
phyllum Broth.) is a synonym of Didymodon tophaceus. I am strongly disposed 
to believe that Didymodon tophaceus, which is also of European distribution, 
is the highest link in a chain of naturally related forms starting with the two 
(or three?) European species of Weisiodon (Gyroweisia) and including as inter- 
mediate forms of whatever rank the Mexican Haplohymenium (Gyroweisia) and 
the Bolivian Gyroweisia, whereby it may be remarked that the others can as well 
or better be understood as secondary phylogenetic developments, by reduction, 
from the higher type of the more widely distributed Didymodon tophaceus. 
As my conclusions are essentially negative, I shall not discuss in further 
detail the characters of the various species referred to, but leave my results as a 
suggestion to the future monographer, who among this as among many other 
groups of mosses is at present more needed than the species or genus-maker. 
To recapitulate briefly, my conclusions are: 
1. Gyroweisia Schimper, 1876, is antedated by Weisiodon Schimper, 1855, 
and should be relegated to synonymy. 
2. Gyroweisia tenuis does not occur in North America, reports of it being 
due to errors of identification. . 
3. Gyroweisia Barbula, G. barbulacea, and G. obtusifolia from tropical or 
subtropical North America do not belong in this genus (Weisiodon) . 
4. I have expressed the subjective opinion, backed by no detailed statement 
of facts, that if Weisiodon is to be extended beyond the original European (and 
North African) application, it should most naturally include the moss known as 
Didymodon tophaceus and related forms. 
Ithaca, N. Y. 
A PRELIMINARY REPORT ON THE LICHENS OF WESTERN PENNSYL- 
VANIA 
Giovanni I. Giardini 
In connection with my candidacy for the degree of Master of Science in 
the University of Pittsburgh, my thesis was written on the Lichens of Western 
Pennsylvania. The following annotated list presents briefly the main results 
of this study. ^ 
1 An examination of Mr. Giardini's list emphasizes that the lichen flora of the region embraced 
is very imperfectly known. Many of the species are represented by but a single collection and one 
can but wonder how many more species are here but have so far been overlooked. It is not at all 
improbable that, with the wanton denudation and waste of much of our area that was once densely 
forested, the lichen flora is radically changed and probably is actually increasing in number of 
species. A large number of the Lichens are preeminently pioneers in denuded or bare habitats, 
such as bare soil and rock, and it is certain that the extent of this kind of habitat at least has 
been much enlarged. Our Cladonia flora, at least, has a much more extended area suitable for it 
