488 MR. E. S. SALMON: REVISION 
In 1859 Mitten (1) placed both these in Leptotrichum under 
the name of L. himalayanum, Mitt., but in 1888 (8) referred to 
this moss as a true Symblepharis, and there are specimens in the 
Kew Herbarium named by him, in 1891, Symblepharis himalay- 
anum, Mitt. There is a fine series of this Indian moss in the 
Kew Herbarium, and an examination of this has led me to the 
conclusion that there is nothing to separate the specimens from 
S. helicophylla, Mont. 
Hooker's original figure and description of Didymodon vagina- 
tum are not full enough to be of much value, but as far as they 
go eohtain nothing unfavourable to the view of the identity of 
the two. At first sight the Indian specimens seem to differ in 
having, often, a shorter capsule, seta usually solitary, and almost 
or quite entire leaves with the nerve frequently quite smooth 
at back. But in many cases the capsules of the Indian spe- 
eimens are longly cylindrical, and, on the other hand, some 
Mexican examples of S. helicophylla have a somewhat elliptical 
capsule. 
The number of setz arising from a perichetium varies from 
one to three—rarely four or five—in Mexican S. helicophylla ; 
in the Indian moss it is usually one, but sometimes two. I do 
not think this difference important, especially asin the American 
S. Oerstediana, C. Müll., which, as mentioned below, Mitten 
considers a form of S. helicophylla, the seta is solitary, just as 
is usually the ease in the Indian specimens. As regards the 
leaves, although those of the Indian plants differ, generally, in 
the points noted above, there are many exceptions. In the 
specimen at Kew labelled ** Leptotrichum himalayanum, Mitt., 
no. 112, Herb. Ind. Or. Hook. fil. & Thomson, Coll. J. D. 
Hooker," the leaves agree in the serrate margin and nerve 
prominently rough at back with those of typical S. helicophylla ; 
and between such leaves as these and the smaller entire ones of 
many of the Indian specimens a complete series of intermediates 
can be found. In the peristome, areolation, inflorescence, &c., 
I can find no constant difference separating the Indian plant from 
the Mexican. 
It is interesting, with regard to the question of the identity 
of these two mosses, to find among Schimper's MSS. preserved 
at Kew some notes on a moss which commence, “ Didymodon 
vaginatum, Hook., Journ. of Bot. vol. ii., et Hook. Icon. Plant. 
