24 HOW TO KNOW THE MOSSES 



the stems generally erect and not much branched, and 

 the fruit at the apex of the stem ; Division B including 

 the pleurocarpous mosses with the stems generally 

 prostrate and much branched and the fruit on the side 

 of the stem. 



As is to be expected with any key based on general 

 characteristics, certain exceptions may be found and 

 certain difficulties encountered. The chief of these are 

 as follows : Mosses coming under Division A may not 

 be strictly erect and may be more or less branched, but 

 the fruit is terminal, although it may appear lateral by 

 the time it is mature on account of the new growth of 

 the stem, which is not so dark a green as the older part. 

 The fruit of Fissidens (p. 97) may be terminal or lat- 

 eral, but the stems are erect and little branched. The 

 stems of the Grimmiaceae (p. iii) and the Orthotricha- 

 ceae (p. 116) may be more or less prostrate with erect 

 branches, but the fruit is borne at the tip of the stem or 

 branch. There are a few erect mosses that come under 

 Division B, but the fruit is always lateral and the 

 stems are usually much branched. 



If a moss has more than one habitat it is placed in 

 the Keys under more than one head; for instance, under 

 "Plants growing on the ground" and ''Plants growing 

 on rocks," etc. 



Leaves of moist plants are described. In Division A, 

 when the leaves are so small that the relative shape 

 cannot be estimated, the mosses are classed under 

 ''Shape of leaves when moist not easily seen." If the 



