8 HOW TO KNOW THE MOSSES 



plants do not show a distinct upper and lower surface. 

 A midrib may or may not be present. In many species 

 it can be seen when the plants are held to the light. In 

 the genus Fissidens (p. 97) the leaves are in only two 

 rows and mHomalia (p. 186) nearly in two rows, but 

 they do not curl under at the tips as the leaves of he- 

 patics so often do. In some other mosses the leaves 

 appear to be in two rows, as they turn in two opposite 

 directions and are somewhat flattened, but in these 

 cases the shape of the leaves or the presence of the fruit 

 helps to distinguish the plants. The mosses are more 

 numerous than the hepatics. 



On account of the importance of distinguishing 

 certain hepatics, the following table may be helpful : — 



Leafy Hepatics Mosses 



{Jungermanniales) 



Plants Always flattened, with Not always flattened, usually 

 two distinct surfaces; the without a lower or back surface, 

 lower or back surface to- 

 ward which the leaves 

 curl sometimes bearing 

 what appear to be root- 

 lets. 



Leaves Arranged in two oppo- Usually arranged equally 

 site rows; rounded, lobed around stem; never lobed or cleft 

 or cleft, often curved un- and when rounded not curved 

 der at tips. under at tips. 



Midrib Absent. Present or absent. 



Classification and Life History 



The mosses, or Musci, and the liverworts, or He- 

 paticae, are the two divisions of the Bryophytes, a Class 

 coming between the fungi and the ferns. The mosses 



