HARDWICKE'S SCIENCE-GOSSIP. 



217 



LICHENS, AND A POLLUTED ATMOSPHERE. 



URING the spring 

 of the present year, 

 I was very much 

 struck with the 

 disastrous effects 

 of a deleterious 

 atmosphere on the 

 growth of lichens. 

 At the same time, 

 I felt very forcibly 

 the confirmation 

 of the fact that 

 these humble 

 plants, so beauti- 

 fully covering na- 

 ture's less graceful 

 parts, as well as 

 pioneering a 

 higher vegetable 

 growth, are them- 

 selves aerial plants. 

 What the water with its solutions is to the Algre, so 

 the air with its chemical substances is to the lichen. 



If the latter fed and nourished its growth through 

 its rhizinre or from the matrix, we should be at a 

 loss to understand the utter obliteration of plants 

 in the same circumstances which once flourished 

 in fruited luxuriance. Growing with other plants in 

 the same place, if it nourished itself in the same way, 

 we should naturally expect the lichen to hold its own 

 with its fellows, subject, of course, to those changes 

 which come alike to all vegetable life ; but it is not 

 so. The lichen will entirely disappear from a spot 

 without any observable change in the other vegeta- 

 tion around, and that from a pollution of the air 

 which is not sufficient to affect those plants which 

 nourish themselves from the soil or matrix of growth. 

 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 growing in the woods at Gibside, Durham. 

 Amongst the plants enumerated is Evernia prunastri 

 (L), 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 

 No. 178. 



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 beautifully 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 seemed to be Peltigera malacea, 

 but it was not in fruit, and a few of the commoner 

 forms of Lecanora and Lecidea. Gibside Woods, 

 barring the atmosphere, are favourable enough for the 

 growth of fructiculose and foliaceous lichens, but for 

 any of these forms I searched them in vain. Not a 

 trace of the series Ramalodei could I find. The trees 

 were as barren of Usnea, Ramalina, and Evernia as if 

 they had never known them, and I might say of 

 almost every other form. I found here and there on 

 an old fir a few barren patches of the thallus of some 

 Calicium, and I noticed a few forms of Lecanora and 

 Lecidea by the river side. 



The lichens which flourished here in the fine 

 condition spoken of by Winch have perished, and 

 this evidently from the pollution of the atmosphere 

 by the smoke and fumes from the Tyneside, and the 

 collieries of the surrounding district. Though these 

 are a considerable distance from Gibside, yet the 

 deleterious elements travel on the wind, for the trees 

 have that dusky coating on their trunks and branches 

 which is peculiar to trees bordering a town, and 

 which is fatal to lichen -growth. 



Gateshead-on-Tyne. W. Johnson. 



SKETCH OF THE GEOLOGY OF HAYES 

 COMMON, KENT. 



By George Clinch. 



HAYES COMMON is pleasantly situated in one 

 of the most beautiful parts of West Kent, 

 about two miles from Bromley. It is bounded on the 

 south and west by valleys, and forms a gently 

 inclined plane dipping to the north and north-west. 

 The subsoil mostly consists of pebble beds, which are 

 composed of light brown quartz sand and well-rolled 

 flint pebbles of various shapes and sizes. These beds 



