136 HOW TO KNOW THE MOSSES 



eral appearance, having erect, fertile stems and pros- 

 trate or arched sterile shoots (Plate VI, Fig. i) ; but the 

 different species cannot be determined without the use 

 of a lens which will show if the teeth are single or 

 double, long or short, and how far they extend around 

 the leaf. Certain species will often bear clustered fruit. 

 It is not unusual to find plants with the leaves forming 

 conspicuous rosettes at the end of the stems. (Plate 

 VI, Fig. I.) These are usually the male plants and the 

 male reproductive organs can be seen in the center of 

 the rosette. See end of this genus for comparison with 

 Rhodobryum, which also has conspicuous rosettes. 



Mnium hornum L. (Plate VI, Fig. 4) is frequently 

 found on moist banks and rocks, especially along streams 

 in woods. It often grows extensively in wide patches, 

 but the fruit is not common. The leaves of this species, 

 unlike those of other Mniums, are long and narrow, 

 usually closely set and erect, sometimes more or less 

 flattened and not much crisped when dry. They are 

 usually a rather dark green. See Fissidens (p. 97) and 

 Aulacomnium heterostichum (p. 140), that have leaves 

 flattened, and Catharinaea (p. 156), that has leaves 

 crisped when dry. 



Range, Newfoundland to Wyoming, south to Georgia; 

 Europe; Asia; Africa. 



The two following species are the largest Mniums. 

 They will be found in swamps and very wet woods, 



