22 HOW TO KNOW THE MOSSES 



comes detached and falls off when the spores are ripe. 

 It may be convex (Plate IV, Fig. 19), cone-shaped 

 (Plate IV, Fig. 20), short-beaked (Plate IV, Fig. 21), 

 or long-beaked (Plate IV, Fig. 22). 



Underneath the operculum surrounding the mouth 

 of the capsule, there is usually a tiny fringe called the 

 peristome which may be single or double. The outer 

 peristome is composed of filaments called "teeth" that 

 are sensitive to moisture; they usually shade from red 

 to orange or yellow. The inner peristome is more 

 dehcate than the outer, and its divisions are called 

 "segments." In wet weather the teeth are tightly 

 closed together to prevent the spores from being 

 washed out in masses; when dry, they separate and 

 bend back allowing the spores to sift out. The number 

 of teeth, and their size, shape, and character are often 

 important points in determining species when studying 

 mosses with a microscope. (See Plate V, Fig. 6 ; Plate 

 VI, Fig. 2; Plate VII, Fig. 4.) 



