194 LICHENS. 



various barks, their worth or worthlessness. Some of 

 these epiphytes are discovered on particular officinal barks, 

 and not on others ; enabling us thus to distinguish them ; 

 while peculiar lichens or fungi make their appearance, 

 as soon as these officinal barks have lost their value; and 

 thus stamp, as it were, the broad arrow of condemnation 

 on them. These symbols of creation, therefore, when 

 rightly interpreted, become a valuable key to practically 

 useful knowledge. 



Upon the bark of a tree in that charming Kentish 

 wood, I descried another kind of lichen, with a thin 

 grey crust, round black receptacles, and a tiny light dot 

 in the centre. This was the gem-like Wart lichen 

 (Verrucaria geminata) a member of the family named, 

 because of their crust being covered with minute warts. 

 A black stem covering the upper surface of a stone beside 

 the brook, showed, through the lens, a similar structure ; 

 and, after careful examination, I was satisfied that it was 

 the black wart lichen (V. nigrescens). 



Another species of this family I found subsequently. 

 While staying in Swaledale a party of us rambled to the 

 village of Healhaugh. Some went to visit the cottagers, 

 who counted much on such occasional courtesies ; and 

 the rest wandered in the fields in hopes of finding some- 

 thing to acid to our botanical collection. A purling 

 brook ran at the back of the village, hurrying from its 

 source among the limestone rocks on the purple moor, 

 yonder, to join the Swale, which was gliding serpent like 

 along the broad lap of the valley. This brook was 

 fringed with Broaklime, and Water Figwort, and Water- 



