94 MOSSES AND LIVERWORTS 



slightly raised in the centre, thus forming a minute 

 excrescence. These papilla, as they are called, are 

 best seen, either when the leaf is viewed in profile, 

 or when the margin is turned inwards or out- 

 wards, and, needless to say, a lens of considerable 

 magnifying power is required for the purpose. 

 At Plate IV. fig. 24 a portion of the leaf of the 

 Smaller Hairy Screw-moss (Tortula lavipila), a 

 tree-loving plant, is given, magnified fifty-one 

 times, and here the roughened surface due to the 

 presence of these papillae is very clearly shown. 

 Another instance of the same thing is depicted 

 at fig. 25 of the same plate, from the leaf of 

 the Spiral-fruited Extinguisher-moss (Encalypta 

 streptocarpa) , a frequenter of limestone walls and 

 banks ; while at fig. 26 a small piece of one of 

 the same leaves is figured, still more highly 

 magnified. 



Another point of interest to be noticed in con- 

 nection with the leaf is, that it always grows 

 directly on the stem or branch, and is never 

 provided with a leaf-stalk, like the leaves of our 

 trees and shrubs. In some cases the base of the 

 leaf is continued, on each side, for some little 

 distance down the stem or branch on which it 

 grows, and is then said to be decurrent (i.e. running 

 down), a feature of much importance in the 

 identification of many mosses. 



Paraphyllia. In some of the Feather-mosses 

 (Hypnacece) , in addition to leaves, the stems bear 



