16 MOSSES AND LIVERWORTS 



which have become entangled among the leaves, 

 glistening brightly in the sun. 



It is almost needless to say that no hard-and-fast 

 line can be drawn between the rock-loving mosses, 

 to which I have just referred, and those that I 

 am for convenience classing as wall-dwellers, for 

 in many instances it seems to be quite a matter 

 of indifference whether a habitation shall be 

 sought on wall or rock. The well-known "Wall 

 Screw-moss (Tortula muralis, Plate II. fig. 10) is 

 the commonest of our wall-growing mosses. So 

 hardy is it that it will flourish even in the near 

 neighbourhood of a town, and almost any wall, 

 that is not quite too close to the smoke, and that 

 has even the most meagre attractions to offer 

 in the shape of a home, is pretty certain to be 

 inhabited by it. It is easily recognised by the 

 form of its leaves, which are rounded, or obtuse, 

 at the end (spathulate, or spoon-shaped, in 

 botanical language), each leaf being moreover 

 terminated by a delicate, transparent hair, which 

 is really a prolongation of the 'midrib or "nerve," 

 as it is called, of the leaf. When a number of 

 these plants grow close together, as is frequently 

 the case, these hair-points give quite a grey or 

 hoary appearance to the green tuft. Plate VII. 

 fig. 25 is a drawing of a leaf on a larger scale. 

 The Grey-cushioned Grimmia (Grimmia pul- 

 vinata, Plate II. fig. 13) is another instance of a 

 common wall-growing moss, with hair-points to 



