MOSSES. 



There are three rows of these leaves, and this is true of most of 

 the mosses. 



249. Habit of mnium. The mnium plants usually form 



quite extensive and pretty mats of green in 

 shady moist woods or ravines. Here and 

 there among the erect stems are prostrate 

 ones, with two rows of prominent leaves 

 so arranged that they remind one of some 

 of the leafy-stemmed liverworts. If we 

 examine some of the leaves of the mnium 

 we will see that the greater part of the 

 leaf consists of a single layer of green cells, 

 just as is the case in the leafy-stemmed 

 liverworts. But along the middle line is 

 a thicker layer, so that it forms a dis- 

 tinct midrib. This is characteristic of 



Fig. 128. 



Portion of moss plant of Mnium affine, showing two 

 sporogonia from one branch. Capsule at left has just 

 shed the cap or operculum ; capsule at right is shedding 

 spores, and the teeth are bristling at the mouth. Next 

 to the right is a young capsule with calyptra still attached; 

 next are two spores enlarged. 



the leaves of mosses, and is one way in which they are sepa- 

 rated from the leafy-stemmed liverworts, the latter never having 

 a midrib. 



