AND BUXBAUMIA. 339 



inner membrane, with a loose cellular or rather spongy 

 substance interposed between the lamellee. 



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 peg 

 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 Dawsonia 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 Gi/m- 

 nostomum pyriforme} 



The quadrangular or four-winged columella of Po/^^nc^wOT 

 commune is well figured and described by the accurate 

 SchmideP ; 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 alse 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. urniyerum, and in a new species very nearly related 

 to it {P. microstomum, nob.) lately received from Dr.Wallich: 

 and the alse of the columella, as far as I have observed, never 

 form complete septa, at least in the ripe fruit ; though [wo 



' Fundam. Hist. Nat. Muscor. Prond. pars ii. tab. 2, /3. 

 = Icones pi. p. 2.36, tab. 59, fig. 15. 



