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 Gymnostomiim, 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 Bryum 

 macrocmyum, whose striking resemblance to Lej^tostomiim 

 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 Bryum 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 Fteroyo- 

 niiim, 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 l)y 

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

 figures, that some at least of his Pterofjonia were of the 

 same structure ; a point that I have not at present 



^ Pterogoiiiuai decliiiatuui. Trans. Linn. Soc. ix, p. 300. 



