POLYTRICHUM. 47 



at its junction with the capsule ; lid with a short rostellate beak. 

 Male plants shorter, with shorter leaves, repeatedly proliferous 

 from the centre of the perigonia. 



Var. /?. perigoniale B. & S. (P. perigoniale Michx.). More 

 densely tufted, with shorter stems ; inner perichsetial leaves very 

 long, with an elongated, almost entire arista. 



Var. y. minus Weis (vars. minus and fastigiatum, Braithw. 

 Br. M. Fl.). More slender, simple or fastigiately branched ; cap- 

 sule smaller and shorter, almost cubical ; lid with a short straight 

 beak. 



Hab. Marshy moors and peat bogs. Common. The vars. j8, y, in drier spots, 

 less frequent. 



Superficially, P. commune much resembles P. juniperinum, the var. perigoniale 

 especially, but the serrated leaf margin will reveal its identity, even without the aid of 

 a lens. Its difference from the preceding species is much less marked, but the more 

 shortly rectangular, more distinctly apophysate capsule will generally identify it, and in 

 any case the form of the marginal cells of the lamellae will always prove a reliable 

 character. 



The var. minus in its unbranched, slender state, is an analogous form to the sub- 

 species strictum of P. juniperinum. The var. fastigiatum would seem only to be a 

 state of this variety. 



P. commune is one of the most highly developed and perhaps the finest of our 

 mosses ; it is one of the few species that is put to some practical use, being collected 

 in Lapland for pillows and beds, both by the Lapps themselves and, according to 

 Withering, by the bears. In this country it is occasionally used for stuffing mattresses 

 and for brooms. 



Order V. BUXBAUMIACEyE. 



Plants very small, almost or quite stemless, growing on earth 

 or rotten wood. Capsule very large in proportion to the size of 

 the plant, oblique and asymmetrical. Calyptra very small, conical; 

 peristome single or double, the outer teeth when present originat- 

 ing in several concentric layers of cells, linear, very faintly barred ; 

 the inner a conical plicate membrane with an opening at the top. 



A very remarkable order of mosses, consisting of half-a-dozen 

 species presenting a quaint appearance unlike that of any others 

 of the class, and no less striking in their morphological characters. 

 It is clear from the researches of Lindberg, Philibert, and other 

 bryologists that most of the present types of peristome must have 

 become fixed before the differentiation of the vegetative organs 

 {e.g., the Hypneae, Bryace£ and Mniacese must have had a common 

 parentage from which they derive their uniform type of peristome). 

 In other words, it seems that the evolution of the Sporogonium 

 was prior to that of the Oogonium, and mosses must have 

 originally consisted of a protonema with a highly organised 

 sporogonium, but with very little development of stem or leaves, 



