MOSSES AND LIVERWORTS 



117 



(Fig. 30, A, a) is composed mainly of a spongy green 

 tissue which is also present in the upper part of the 

 capsule, surrounding the large air-spaces between the 

 sporogenous tissue 

 and the outer part 

 of the capsule. This 

 green tissue recalls 

 the " mesophyll ' or 

 spongy green tissue 

 in the leaves of the 

 higher plants, and 

 like the mesophyll 

 communicates with 

 the outside atmos- 

 phere by stomata. In 

 a few cases, this basal 

 part of the capsule 

 (apophysis) is a very 

 much enlarged spe- 

 cial organ, comparable 

 physiologically, al- 

 though hardly struc- 

 turally, with the 

 leaves of higher 

 plants. 



The formation of 

 spores is restricted to 



FIG. 30 (Musci). A, a longitudinal section 

 through the upper part of the sporophyte 

 of Fuharia; a, the apophysis or en- 

 larged basal part of the capsule, con- 

 taining chlorophyll and with stomata 

 in the epidermis; sp, the sporogenous 

 tissue; o, the operculum, or lid, which 

 finally falls away and allows the escape 

 of the spores ; r, the ring of cells where 

 the lid o separates from the urn, or 

 theca; B, cross-section of a young cap- 

 sule, showing the position of the sporo- 

 genous cells; C, a young stoma or 

 breathing pore from the base of the 

 capsule. The structure of the stoma is 

 like that found upon the leaves of the 

 higher plants. 



a very small part of 



the sporophyte, the sporogenous tissue comprising but a 

 single layer of cells forming a cylinder in the middle 

 region of the capsule, and surrounding the central col- 

 umella (B, sp). The upper part of the capsule usually 



