BBYOPHYTES 



295 



capsule beneath the epidermis are green and are therefore able 

 to carry on some photosynthesis, but the greater part of the food 

 required for the development of the spores within the capsule 

 is derived from the mother plant through the seta. 



When the spores are ripened, the inner tissues of the capsule 

 break down and the spores lie free within its central cavity. 



-Seta 



FIG. 164. Stages in the development of the sporophyte in Funaria 



a, archegonium containing the cellular embryo of a young sporophyte ; b, moss plant 

 with rodlike emhryo still in the expanded archegonium ; c, rod stage of the sporo- 

 phyte with the old archegonium wall, neck, and venter ; d, mature sporophyte with 

 parts differentiated ; e, parts of the capsule ; /, portion of the peristome ; g, gameto- 

 phyte and sporophyte in proper relation 



The mature capsule at this time consists of the following struc- 

 tures, represented in Fig. 164, e and /. A lid, or operculum, is 

 released at the apex of the capsule, thus exposing the light spores 

 to the air. When the lid is removed, a circle of hairlike teeth, the 

 peristome, is seen to guard the mouth of the capsule. These teeth 

 have the power of movement and tend to close over the mouth 

 of the capsule 'in wet weather and to open out in dry weather, 

 when the light spores are more easily scattered by the wind. In 

 many mosses the teeth open by chinks in dry weather only, so 

 that the spores are sifted out, like salt out of a salt shaker, 



