148 ABOUT MOSSES AND LICHENS. [CHAP. 



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 atmo- 

 sphere, are favourable enough for the growth of fruc- 

 ticulose and foliaceous lichens, but for any of these 

 forms I searched in vain. Not a trace of the series 

 Ramolodei could I find. The trees were as barren 

 of Usnea, Ramalina, and Evernid 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 con- 

 dition 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." * 



The development of these plants is exceedingly 

 slow, and they take years to come to maturity, owing 

 greatly to the fact that their growth is suspended 

 during dry weather. There is little necessity to de- 

 scribe them, as all are acquainted with their grey or 

 yellow incrustations on the rocks of the mountain 

 side, the trunks of trees, and even upon brick walls. 

 But beneath this sober coat of grey they possess a 

 * Science Gossip, 1879, p. 217. 



