Mosses and Lichens 



Twenty-one species are known in all, five in America. 



The Triangular Wood-reveller, Hypnum (Hylocomnium) 

 triquetrum, Linn. See plate XXXII. 



Habit and habitat. In large yellow or light-green mats 4 to 

 8 inches deep, on decayed wood in plains and mountains. 



H. triquetrum. Female plant. 



Name. The specific name triquetrum was given to the moss 

 by Linnaeus to describe its habit of pointing its branches in three 

 directions, the Latin triquetrum meaning "having three angles." 



Plants (gametopbyte). Stems stout and rigid, erect, simple 

 or slightly divided, branched unequally and irregularly or with 

 feather branches not all in the same plane. 



H. triquetrum. Branch leaves. 



Leaves. Very large, horizontally spreading both when wet or 

 dry, stiff and membranous, glossy, triangular; apex acute; vein 



310 



