Mr. Brown on Lyellia, Leptostomum, and Buabaumia. 573 
From the account given of Gymnostomum Griffithianum it ap- 
pears that this species also has in the early stage a membrane 
completely covering the mouth of the capsule. But this mem- 
brane probably differs in origin, at least, from that of Hymenosto- 
mum, as it seems to do both in form and dehiscence from the pe- 
ristomium of Leptostomum. 
Of Gyinnostomum fasciculare I have examined only imperfect. 
specimens, I cannot therefore speak with confidence of its struc- 
ture. The annular process, however, mentioned by Mr. Hooker 
is more likely to be the remains of a complete horizontal covering, 
and probably originating from the inner membrane, than to re- 
semble the peristomium either of Hymenostomum or Leptostomum. 
A membrane of this kind is certainly present in some species of 
Gymnostomum, and perhaps may be found in all those that really 
belong to that genus. It exists also in Weissia Templetoni, which 
so closely resembles Gymnostomum fasciculare as to be with diffi- 
culty distinguished from it, unless by the inspection of the peri- 
stomium ; and, in addition to the erect annular peristomium from 
which the character of the genus is taken, I have observed a simi- 
Jar membrane in Leptostomum itself. It seems even to be not arf 
uncommon process or termination of the inner membrane, though 
it has been remarked only in some of its more obvious and per- 
sistent modifications. Thus the spongy membrane figured and 
described in the two published species of Calymperes, seems to 
be an analogous structure*, as is also the circular disk terminat- 
* The circular spongy membrane covering the mouth of the capsule certainly does not 
form an essential part of the character of Calymperes ; for, in the only species that I have 
examined, it is either entirely wanting, or firmly adheres to the inner surface of the oper- 
culum, along with which, also, a considerable portion of the columella separates. Nor has 
Swartz, who established the genus (in Spreng. Schrad. und Link Jahrb. der Gewäch. 
vol. i. p. 1.) even noticed this membrane in his description. 
AE 2 ing 
