THE HEATH. 91 



this too is a living plant) a rough grey substance,* 

 thickly studded with light-coloured circular disks, 

 having raised borders, not unlike small stemless 

 mushrooms. The plants which I am describing 

 are called Lichens ; and, although many of them 

 are minute, and to a careless observer insignifi- 

 cant, they are, as we shall see by-and-by, of very 

 great importance in the economy of Nature. 



MAP LICHEN. 



These, and a vast number of others, agree in 

 having a rough surface, and in being so intimately 

 attached to the rock as to be practically insepara- 

 ble from it without breaking one or the other. 

 Scattered over the same pile of rocks, you will find 

 others, resembling those described, in being fas- 

 tened to the bare rock without the aid of roots ; 

 but differing in these respects, that their substance 

 is thicker, and that they are not attached by the 

 whole of their under surface, but curl upwards at the 

 extremity. One you will find in great abundance 

 * Lecanora Parella. 



