Lichens found near Painswick. Robert Paulson. 303 



LICHENS FOUND NEAR PAINSWICK. 



22nd-2^th May, 1920. 

 By Robert Paulson, F.L.S., F.R.M.S. 



In so short a period as three days it was only possible to 

 search over a very circumscribed area of the higher ground to 

 the north-west of Painswick. A few species were, however, seen 

 upon the larger trees, beech and ash, in the woods near Birdlip. 



A noticeable feature of the lichen flora of this district is the 

 paucity of corticolous and terricolous species. Those that were 

 gathered proved to be very poorly developed specimens belong- 

 ing to the Pertusariaceae, Cladoniaceae and Graphidiaceae. This 

 feature cannot be explained by saying that it is simply due to 

 the low Hght-intensity within the wood, for shade lichens of the 

 Graphidiaceae are equally rare and stunted in growth as are 

 those belonging to the Parmeliaceae. On the outer borders of 

 the woods, towards the south and south-west, where the light- 

 intensity is considerably higher than it is some distance within 

 the wood, corticolous lichens rarely occur. 



This area is not adversely affected by a great smoke drift, 

 for the trunks and branches of the trees are not begrimed with 

 soot as they would be if subjected to such a baneful influence. 



The only suggestion that can at present be offered to explain 

 the absence of the corticolous species in the woods around Pains- 

 wick, is, that such absence may be due to some edaphic factor 

 of the soil which is as yet unknown to us, for it is highly prob- 

 able that edaphic factors are occasionally inimical to lichen 

 growth within a wood. 



There is a comparatively rich harvest of saxicolous species, 

 shown by the accompanying list, to be gathered on the sunny 

 side of the field oolitic-stone walls and from the rocks project- 

 ing through the soil, when these are sufficiently remote from 

 the clouds of dust that are raised by the heavy motor traffic 

 upon the main roads. The species of the walls are for the most 

 part crustose; there are very few foliose species upon them. 



Tichothecium pygmacu^n Koerb., a fungus parasite, was abun- 

 dant on the thallus of Placodium rupestre. 



