146 Mr. Turner's Descriptions of Eight New British Lichens. 



bare and smooth part of the tree : nor can its fructification be 

 discovered without attentive examination ; for even the shields 

 are by no means of a nature, either from their colour or size, to 

 strike a cursory observer. Mr. Borrer, therefore, suspects, and, 

 as it seems, not without reason, that the gray tinge frequently 

 observable on the bark of old elms belongs in reality to this 

 plant, though neither he nor I were ever able to detect any fruit 

 beyond the borders of Sussex. The nature of the shields is so 

 peculiar, that a few remarks with respect to these is all that it 

 can be necessary to say for the purpose of eifectually discrimi- 

 nating this Lichen from its congeners. They are very different 

 from those of any other Parmelia, and more resemble the apothe- 

 cia of Urceolaria eocanthematica, being almost wholly immersed 

 in the crust, and in their first stage enveloped by the margin, 

 which soon splits into different segments, though not with the 

 regularity observable in that plant, disclosing the flat, yellow- 

 ish, or flesh-coloured disk. In the older shields the margin be- 

 comes worn down, so as to be level with the disk, and is in this 

 state thick, obtuse, uneven, and crenulated ; it is also some- 

 times quite obliterated. The place to be assigned to P. carneo- 

 lutea lit the Methodus Lichcnum is that immediately following 

 P. rubra, from which it is distinguishable by the smoother crust, 

 the colour of the disk of the shields, their immersed situation, 

 and their margin; or, when this is worn away, by the disk being 

 by no means concave, but flat, or slightly convex, with a slight- 

 ly perceptible whitish edge. 



Parmelia Clement i. 



Parmelia thallo crustaceo-membranaceo orbiculari sorcdiato al- 



bido, 



