CRYPTOGAMIA LICHENES. 83 



become obsolete. To the volatile alkali P* omplmlodes im- 

 mediately imparts a tawny -red, and this infusion affords 

 one of the most indestructible of all colours. " The colour 

 remains after the substance that extracted it is gone ; it is 

 not in the least impaired by long exposure to the air ; nor 

 can it be either destroyed or changed by acids, alkalies, or 

 alcohol. A most singular property! as there is no red 

 dye in use that remains unaltered by these powerful li- 

 quors." Dr WALKER. PENNANT tells us, that in 1772 

 it was an article of commerce from the west of Scotland, 

 exported for the use of the dyers, at the price of a shilling 

 or sixteen pence a stone. 



9. P. physodes, imbricated, greyish-white, smooth, beneath 

 glossy black, naked ; ends of the lobes inflated, brown below, 

 HOOK. Scot. ii. 56. LicJien physodes, WITH. iv. 34. Eng. Bot. t. 

 126. DILL. Muse. t. 20. f. 40. 



Hob. On the stems of heath in moors, and on trunks of 

 trees. Lamberton moor. Blackadder plantations, abun- 

 dant. 



" This species is remarkable for being always composed 

 of two membranes, the undermost black, the upper white, 

 with a considerable cavity between them." I have not 

 observed it in fruit. According to Dr WESTRING this 

 lichen is very rich in colouring matter, affording, by means 

 of different re-agents, tints varying from a citron-yellow to 

 chestnut-brown. NEILL. 



46. LECANORA. 



1. L. atra, crust coarsely granulated, thickish, greyish-white; 

 apothecia very black, cupped, with a white elevated border. HOOK. 

 Scot. ii. 47. Lichen ater, LIGHTF. Scot. 813. WITH. iv. 19. Eng. 

 Bot. t. 949. Parmelia atra, SPRENG. Syst. Veg. iv. 295. DILL. 

 Muse. t. 18. f. 15. 



Hab. On rocks and trunks of ash-trees, very common, in 

 round or oval spots. 



The apothecia are numerous, and frequently so crowded as 

 to press on one another. In age they become plane. 



2. L. mbfusca, crust granular, greyish-white, rather thin ; apo- 

 thecia brown with a whitish border, cupped, becoming plane or con- 



