354 DESCRIPTION OF 



iiished with a membrane, exactly as in the species here 

 described, but I could not perceive any remains of external 

 teeth. In opposition to such authority, however, I do not 

 venture to add it to this genus, to which in every other 

 respect it seems to belong. 



The character of Leptostomum, derived from the undivi- 

 ded annular process of the inner membrane of the capsule, 

 may to many appear too minute, and perhaps unimportant ; 

 and had it been observed in one species alone, I should not 

 have ventured on that account to distinguish" it as 

 a genus : but finding it in four species, accompanied too 

 with a habit widely different from that of Gymnostomum, to 

 which these plants must otherwise be referred, I have not 

 hesitated to employ it. As, however, Hedwig has actually 

 figured and described an external peristomium in his Brywni 

 macrocarpum, whose striking resemblance to Leptostomum 

 has been already noticed, there may be still some reason to 

 doubt the sufficiency of the generic character, and it may 

 seem somewhat improbable that Mosses of such a habit 

 should be really destitute of an outer peristomium. But, 

 without questioning the accuracy of Hedwig in this in- 

 stance, I may be permitted to observe, that the outer peri- 

 stomium which he has figured in JBryuni macrocarpum is 

 extremely unlike that of any other genus where the fringe 

 323] is double : and it may perhaps in some degree tend to 

 strengthen the character of Leptostomum, to advert to what 

 appears to be really the case in certain species of Pterogo- 

 nium, in one of which^ Mr. Hooker has already described 

 the fringe as derived solely from the inner membrane ; and 

 I have collected, on the mountains of Van Diemen's Island, 

 a moss with a peristomium decidedly of like origin ; a cir- 

 cumstance that appeared to me so remarkable, that I had 

 actually described it as a distinct genus, before I was aware 

 of the similar structure of the Nepal plant described by 

 Mr. Hooker ; or of the probability, from Hedwig's own 

 figures, that some at least of his Fteroc/onia were of the 

 same structure ; a point that I have not at present 



' Ptcrogoniuni decliiiatuin. Traits. Litui. Sue. ix, p. 309. 



