THE GENEEA OF MOSSES. 
89 
17. The peristome and mouth of the thcca ; shewing 
the crenated margin of the theca,--the outer 
peristome composed of cilise (which are 
usually more or less injured in removing the 
operculum), — and the inner conical membra- 
naceous peristome. 
18. A mature theca divided, and exhibiting the 
same parts as in the corresponding figure of 
Di'physcmmy the only difference being in the 
small pillar which supports the sporular sac 
and columella. It is here dilated into a little 
hollow globe, which nearly fills up the passage 
from the theca to the apophysis, and is again 
contracted and continued down to the base of 
the apophysis. 
19. A sectional view of the two perichsetia, the mouth 
of the theca, the summit of the sporular sac, 
and that part of the columella which is above 
the line at which the sporular sac is attached 
to it. 
50. A leaf taken from near the base of the perichae- 
tium, 
51. The root divided longitudinally. 
SS. The little pillar which supports the sporular sac 
removed. 
Sporules. 
All the figures, except the first, are more or less 
magnified. 
