BRYOPHYTA 



203 



layers of cells. The sporogenous tissue is cut off from the endothecium as 

 the outermost layer of cells, the remainder form- 

 ing a sterile columella. The sporogenous tissue is 

 not continuous over the columella as a dome, but 

 has the form of a hollow cylinder. It may extend 

 to the base of the capsule, as in Polyirichuni, or may 

 not. The sporogenous tissue usually becomes two- 

 layered, all its cells giving rise to spore mother cells. 



As seen in longitudinal section, the mature cap- 

 sule is very complex, being made up of an epider- 

 mis with stomata, several wall layers of colorless 

 cells, an air-chamber region consisting of green 

 tissue, an outer tapetum, the sporogenous tissue, 

 an inner tapetum, an inner air-chamber region 

 (present only in highly specialized forms, such as 

 Polyt7'ichum.) , and a. central columella (Fig. 167). 



The operculum, which forms the upper part of 

 the capsule, is complex in its development (Fig. 168). 



Fig. 166. Embryo of 

 Funaria hygrometrica 

 enclosed by the calyp- 

 tra, X500. {After 

 Sachs.) 



It is often dif- 



-- Peristome 

 — Operculum 



— Columella 



Spore-bearing 

 Tissue 



"WaW 



Air Chamber 



Fig. 167. Longitudinal section of the capsule of Funaria hygrometrica. (From Sinnott.) 



