AND BUXBAUMIA. 339
inner membrane, with a loose cellular or rather spongy substance interposed between the lamellae.
Besides this transverse annular projection there are in the inner membrane of all the species of Polytrichum that I have examined, P. undulatum alone excepted, four longitudinal [569 equidistant processes, extending from the aperture to the base of the capsule ; and in many species projecting so far into its cavity as to come in contact either with the salient angles or sides of the columella, and consequently to sub- divide it into a determinate number of cells.
The analogy of these longitudinal processes with the more numerous and irregular plicae in Daiosonia and Lyellia is obvious ; and I have not myself met with similar processes of the inner membrane in any other genus of mosses. They do not, however, afford an absolutely distinguishing character of this group, as they seem to be altogether wanting in Polytrichum undulatum ; and Hedwig, it must be admitted, has represented an apparently analogous structure in Gym- nostomum pyriforme. 1
The quadrangular or four- winged coliunellaof Polytrichum commune is well figured and described by the accurate Schmidel 3 ; and I have found an equally regular form of this body in most of the species of Polytrichum that I have examined ; though in many it is less evidently winged than in P. commune and the species nearly related to it.
Mons. de Beauvois seems to consider the alae of the columella as themselves forming complete septa, and also that in this state they exist only in such species as have quadrangular capsules ; for to these he limits his genus Polytrichum, distinguished by him from Pogonatum by its multilocular fruit. The cavity, however, is completely sub- divided in several of the species with cylindrical capsules, as in P. urnigerum, and in a new species very nearly related to it (P. microstomum, nob.) lately received from Dr.Wallich: and the alae of the columella, as far as I have observed, never form complete septa, at least in the ripe fruit ; though [570
1 Fundam. Hist. Nat. Muscor. Frond, pars ii. tab. 2, ft. " Icones pi. p. 23G, tab. 59, fig. 15.
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