VI. 



THE BRYALES 



211 



cells, when the capsule is ripe, that effects the separation be- 

 tween the operculum and theca. 



The peristome arises from the fifth layer of cells from the 

 outside of the operculum. If a median longitudinal section of 

 a nearly ripe capsule is examined, the row of cells belonging 

 to this layer (Fig. iii, per), is at once seen to have the outer 

 walls strongly thickened, and this thickening extends for a 

 short distance along the transverse walls. The inner walls of 

 the cells also show a slight increase in thickness, but much less 

 marked than the outer ones. A similar thickening of the cell 

 walls occurs also in about three rows of cells w^hich run from 



Fig. 112. — Longitudinal section of a fully-developed sporogonium of Funaria hygro- 

 metrica, X about 40; s, seta; a, apophysis; sp, spores; col, columella; r, annulus; 

 0, operculum. 



the outside of the capsule to the base of the peristome, and form 

 the rim of the "theca" or urn. 



The epidermis of the whole capsule has its outer w^alls very 

 much thickened, and upon the .apophysis are found stomata 

 quite similar to those found upon the sporogonium of Antho- 

 ceros or upon the leaves of vascular plants. Haberlandt ( (4), 

 p. 464), showed that while the form of the fully-developed 

 stoma in Funaria differs from that of most vascular plants, 

 this difference is secondary, and that in its earlier stages no 

 difference exists. This can be easily verified, and with little 

 difficulty all the different stages found. The young stoma 

 (Fig. 113), has the division wall extending its whole length, 



