Mr. Brown OH Li/cl/ia, Leptosiomum, and Buxbaumia. 565 



spongy texture of the base of the capsule. But by thus removing 

 support from the columella and inner membrane, they may con- 

 tribute to the greater shortening of the former, and consequently 

 in increasing the dispersion by the mouth of the capsule ; or, from 

 the same cause, the inner membrane being at length ruptured, the 

 seeds may be in part discharged by the pores themselves. 



It seems then not improbable, from what we at present know 

 of the structure of LyeUiu, that for the dispersion of the seeds in 

 this genus there are two distinct contrivances, both of which, 

 however, in the only species yet known, are apparently imperfect. 

 But hence it is perhaps allowable to conjecture, that either other 

 species of Lyellia, or a nearly-related genus may exist, in whicii 

 while the mouth of the capsule remains absolutely shut, the pores 

 of the base may be sufficiently enlarged for the complete per- 

 formance of this important function. 



Pores exactly resembling those of L?/eWia crispa have not hither- 

 to been found in any other moss. 1 have observed, however, in 

 several specimens of Polijtrichum alpinum still more minute pus- 

 tules, not very different in appearance, and similarly situated oii 

 the base of the capsule. 



In establishing this new genus of Mosses, it is of importance to 

 determine its more intimate affinities in the family to which it 

 belongs. Its place is unquestionably between Fohjtrichum and 

 Dau'sojiia ; and it will I believe be admitted, that these three ge- 

 nera, in the natural method, cannot be separated ; though they will 

 necessarily form or be referable to distinct sections of an artificial 

 system founded chiefly on modifications of the peristomium. 



In attempting to discover characters by which this group of 

 PoLYTRiCHOiDEM may be distinguished from other Mosses, it is 

 in the first place necessary to determine the whole structure of 

 Polytrichum ; for this genus, though one of the most common of 



4 D 2 the 



