ix.] ABOUT MOSSES AND LICHENS. 147 



though in form many of them resemble some of the 

 Liverworts. Yet though allied to the Fungi, there 

 is no close relation to them. Fungi derive their 

 nourishment from the substances upon which they 

 grow. Not so Lichens. Their food is absorbed 

 from the atmosphere, and it may be taken as a 

 general rule that where Lichens grow the atmo- 

 sphere is pure, for any impurity kills them. They 

 have been observed to disappear entirely from dis- 

 tricts where they formerly occurred in great abund- 

 ance ; and such disappearance has been entirely due 

 to the pollution of their atmosphere by the growth 

 of a manufacturing town, the establishment of a 

 colliery, or other smoke-producing industry. Mr. W. 

 Johnson, in a recent volume of "Science Gossip," 

 gives an instance of the disappearance of a species 

 from the woods of Gibside, Durham. " In Winch's 

 ' Flora of Northumberland,' published in the Trans. 

 Nat. Hist. Society of Northumberland and Durham, 

 1832, mention is made of a number of lichens grow- 

 ing in woods at Gibside, Durham. Amongst the 

 plants enumerated is Evernia prunastri, said to be 

 in fructification in Gibside Woods. As I have never 

 had the pleasure of gathering this species in fruit in 

 any part of North Durham, or the west and south of 

 Northumberland (which I have more or less searched) 

 I went out to Gibside in the spring to see if I could 

 find the above lichen. Gibside is some seven miles 

 from Newcastle to the south-west. The hall is beau- 

 tifully placed on the Derwent. The surrounding 

 woods run back on to Whickham Fell. On the 

 latter I found one or two forms of Callema, and what 



