PAHMELIA. 



213 



must, at some period of its life, have been fixed to, or deve- 

 loped from some base of support ; for we shall afterwards 

 see that Pallas, and Eversmann, and other Asiatic travellers 

 assert that the manna Lecanoras of the neighbourhood of 

 Lake Aral are free ah initio, and never contract any attach- 

 ments or adhesions. The testimony of travellers, in regard 

 to the occurrence of erratic Lichens having a free or non- 

 adherent thallus, has hitherto been received with consider- 

 able suspicion ; it is now however corroborated by the ex- 

 istence of this erratic Parmelia in Britain. 



We have seen only barren specimens ; and, in the absence 

 of the fructification, the species to which the plant belongs 

 cannot be accurately determined. Its characters approxi- 

 mate it most closely to P. pulcliella, var. ccesia. The thal- 

 lus is whitish-glaucous, smooth, shining, occasionally exhi- 

 biting a few scattered, punctiform, white soredia, cartilagi- 

 nous-membranaceous, — below brownish, with brown fibres ; 

 lacinise vary in size and mode of division, are very convex, 

 much curled and twisted at margins, many of them broad- 

 ened and rounded at their apices. 



The genus Parmelia includes some of the largest and 

 most handsome both of foreign and native Lichens. The 

 Parmelias have been popularly denominated the "Leaf 



