Mr. Brown oh LyelliOy Leplostomitm, and Buxbaumia. 573 



From the account given of Gymnostomum Griffdhianum 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 diflers in origin, at least, from that of Ilymenosto- 

 mum, as it seems to do both in form and dehiscence from the pe- 

 ristomium of Leptostomum. 



Oi Gymnostomum 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 JVeissia 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- 

 lar membrane in Leptostomum itself. It seems even to be not an 

 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 lerminat- 



* The circular spongy membrane covering the mouth of the capsule certainly does pot 

 form an essential part of the character x>f 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. Sckrad. und Link Jahrb, der Gewdeh. 

 vol. i. p. 1.) even noticed this membrane in his description, 



4 E 3 ing 



