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sfomum tenue by Drummond.^ Wilson in his critical notes on Drummond's 
first sef suggested that this specimen might be Gymnostomum calcareum, and 
such in fact it appears to be. The two species have been much associated with 
one another, because their stems and leaves are so reduced by xerophytic condi- 
tions of growth that they closely resemble each other. Their capsules are how- 
ever distinct, those of Gyrowetsia tenuis being distinguished by a large persistent 
annulus. So persistent is this that it will usually be found even on old deoper- 
culate capsules. I have not been able to find a trace of it on any of Drummond's 
capsules and have no doubt that they are those of G. calcareum, as Wilson took 
them to be. To confirm the identity I have also sought gametophyte characters. 
These are very hard to make out, so great is the reduction of the vegetative 
parts in both mosses. The stem of G. tenuis I find in section without central 
strand, as noted by Limpricht,^ while that of G. calcareum has a central strand 
with a layer of rather large cells surrounding it, as in G. rupestre. Drummond's 
specimens are not very favorable for this kind of investigation, but I think there 
is no question but that they have the stem-section of G. calcareum. The section 
of the leaf-costa has so little character in these reduced plants that I cannot 
regard it as conclusive, but I see nothing in Drummond's plant in this respect to 
separate it from G. calcareum. There is no satisfactory doubt that Drummond's 
Canadian specimen is G. calcareum, and the same is still more , clearly true of 
other Canadian specimens referred by Macoun and Kindberg to Gymnostomum 
tenue, also of those referred to Gymnostomum pusillum Kindb. (Gyroweisia 
pusilla Broth.). I have also seen specimens from the Ottawa Herbarium labeled 
Gyroweisia reflexa, but they are also G. calcareum, except one which is a Seligeria. 
Confusion of the two species by European bryologists is apparently not in- 
frequent; in fact the European specimen in the Ottawa Herbarium labeled 
Gyroweisia tenuis, collected by Artaria in northern Italy, is also Gymnostomum 
calcareum. Kindberg's Gyroweisia linealifolia^ from Switzerland is also according 
to Paris^ Gymnostomum calcareum. The Gyroweida tenms distributed by Hol- 
zinger in his exsiccati (No. jji) from Enfield Gorge, N. Y. proved to be a sterile 
specimen of the moss variously known as Diphyscium folio sum or Wehera sessilis, 
the correction having already been made by Holzinger in his privately printed 
notes. 
Only the most thorough-going monographical work with consideration of 
all related mosses of the world can justify and, having justified, properly delimit a 
genus Weisiodon Schimper. That the exotic species included by Brotherus 
(in Nattirliche Pflanzenfamilien) are not those of most immediate relationship 
5 Careful study of the literature concerning Drummond's collections (Cf., for example, Hooker, 
Botanical Miscellany, 1, 93. 1828; Hooker, Journal of Botany, 111, 433f. 1841) shows that he 
was himself responsible for the naming of his first set of American mosses, except in so far as 
certain new species are definitely accredited to Hooker. 
6 Hooker, Journal of Botany, 111, 434. 1841. 
''^ Laubmoose, 1, 235. 1886. 
8 Rev. Bryol., XIX, 104. 1892. 
* Index Bryol., ed. 2, 11, 293. 1904 
