66 



MOSSES 



The peristome consists of a number of hygroscopic tooth- 

 like projections called peristome teeth. These teeth are so 

 constructed that when the air is moist they absorb water 

 and bend inward to cover the epiphragm; when the air is 



FIG. 32. Musci. Upper left figure is a longitudinal section of an anthe- 

 ridial head. The upper right figure is a longitudinal section of an empty 

 antheridium and immediately below a cross-section of an antheridium filled 

 with sperms. The lower left figure is a longitudinal section of an arch- 

 egonial plant. The lower right figure is a longitudinal section of an arch- 

 egonium with egg cell. 



