MOSSES 93 



from those produced on the upper part, though 

 this is not by any means of frequent occurrence. 



With regard to the curious hair-point to the 

 leaves of certain mosses a very good illustration 

 of which is to be found in the dark green, spoon- 

 shaped leaves of our old friend the Common Wall 

 Screw-moss (Tortula muralis) this varies in length 

 in different species, being sometimes so long as 

 to impart quite a hoary appearance to the tufts, 

 as, for instance, in the case of the well-known 

 Grey-cushioned Grimmia {Grimmia pulvinata, 

 Plate II. fig. 13). The microscope discloses that, 

 in some cases, it is quite smooth, as in the one 

 drawn, on a large scale, at Plate VI. fig. 20, from 

 a leaf of the Wall Screw-moss (Tortula muralis) ; 

 while in others its surface is roughened owing to 

 the presence of minute teeth, as at fig. 21 of the 

 same plate, taken from a leaf of another member 

 of the same family. In one British moss the 

 apex of the leaf is still more specialised, for it 

 terminates in a curious double hook, thus enabling 

 us at once to recognise this particular species. 

 This moss is known as the Pendulous Wing-moss 

 (Antitrichia curtipendula) ; it grows chiefly on 

 rocks and trees in mountainous districts. A leaf 

 is given at fig. 26 of Plate VII., and the apex 

 more highly magnified, and showing the double 

 hook, at fig. 30. 



The surface of the leaves is not unfrequently 

 roughened, owing to the fact that each cell is 



