Muscologia Itineris Assamici. 469 



has nothing in common with the usual form of mosses, in which 

 both peristomes originate from the inner membrane. In the 

 genus alluded to, and in one or two allied genera, it is an 

 extension of the outer wall of the capsule, shews usually 

 no indications of composition, and is probably analogous 

 to the annulus of the more developed genera of the order. 

 Its processes too are liable to vary in number, and they are 

 in some species much increased beyond the number 32, which 

 is the maximum number of a single peristome of the usual 

 structure, in which likewise no instance occurs of less than 

 16; for although Tetraphis has only four, and one or two 

 genera only eight teeth, the composition, as indicated by lon- 

 gitudinal lines, is in all such 32. The smallest number, 16, 

 exists in some Weissiae and Didymodons. I believe that 

 Mr. Brown was the first to direct attention to the com- 

 position of the teeth of the peristome in the above instances. 

 One of the most curious peculiarities in Polytrichum exists 

 in the inflection of the inner membrane, forming, as it were, a 

 ring opposite the neck of the capsule. This is quite distinct 

 from the inflection that occurs in some other genera, in 

 which the inflected portion is the termination of the mem- 

 brane. 



The outer peristome of Buxbaumia is obviously of ana- 

 logous origin with the peristome of Polytrichum; neither 

 do I see any reason for not adopting the opinion of Bridel, 

 that the inner peristome of Buxbaumia and Diphyscium is 

 analogous to the epiphragma of Polytrichum. Bridel in his 

 generic characters of Catharinea, Pogonatum and Polytric- 

 hum, describes the teeth of the peristome as seizing, by their 

 apices, the epiphragma. This is incorrect ; the teeth are 

 seized by the epiphragma, which, in the dry state alone by 

 contraction, leaves the interstices open: in the wet state it 

 expands, covering the whole of the teeth as well as their in- 

 terstices. 



I have referred a species, which, with almost every charac- 



