258 PLANT LIFE. 



covering is retained and is able to open and shut auto- 

 matically according to the dryness or wetness of the 

 atmosphere. In Funaria and most mosses this latter 

 covering consists of (3) a series of peristome teeth, 

 which are triangular or of the shape of a segment of 

 a circle. These teeth are hygroscopic and curl inwards 

 in wet weather but twist outwards in dry weather so 

 that the spores can escape. Even, then, however, the 

 spores are only scattered if the capsule stalks are 

 vigorously shaken. 



Polytriclium differs in having the central parts of 

 these peristome teeth joined together making a circular 

 white membrane. The spores can only escape through 

 the pores between the teeth ; and will, obviously, only 

 escape in dry weather, and in small numbers. Thus 

 the scattering of the spores takes a much longer time 

 in Polytrichum. 



Mosses generally grow in one of two ways. Either 

 the stems are erect with very few branches and are closely 

 set in little tufts as in the case of most mosses found 

 on walls, or the branches are prostrate or curving over 

 and finely divided in a feathery manner like the 

 Hypnoids or mosses found on the soil in woods and 

 upon tree bark. There are one or two exceptions 

 such as Fontinalis and Climacium which will be separately 

 mentioned, but the vast majority grow in one or other 

 of these two ways. 



The tuft-mosses on walls are especially interesting. 

 They begin to grow upon the mortar between the 

 stones or upon the remains of lichens which have, 

 prepared a footing for them ; and on any old wall there 

 are generally quantities of these little tufts, consisting 

 of very small upright stems with closely set leaves 

 crowded together. If you break the tuft away from 



