Mr. Brown on Lyellia, Leptostomum, and Buxbaumia. 569 
P. undulatum alone excepted, four longitudinal equidistant pro- 
cesses, 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 colu- 
. mella, and consequently to subdivide it into a determinate num- 
ber of cells. 
= The analogy of these longitudinal processes with the more nu- 
merous and irregular plicze 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 ana- 
logous structure in Gymnostomum pyriforme*. 
The quadrangular or four- winged columella of Polytrichum com- 
mune is well figured and described by the accurate Schmidel+; 
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 spe- 
cies 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 cap- 
sules; for to these he limits his genus Polytrichum, distinguished 
by him from Pogonatum by its multilocular fruit. The cavity, 
however, is completely subdivided 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 re- 
ceived from Dr. Wallich: and the ale of the columella, as far as 
* Fundam. Hist. Nat. Muscor. Frond, pars ii. tab, 2. 6. 
+ Icones pl. p. 236. tab. 59. fig. 15, 
I have 
