1857.] DESCRIPTIONS OF NEW BRITISH LICHENS. 107 



granular, incurved, crenate. — Lichen cseruleo-badius, Schl. Crypt. 

 Helv. Parmelia rubiginosa, ^, Schar. ^pic. 469 {eoccl. Dill. Syn.) ; 

 Enum. Crit. 36. Lichen lanuginosus, Iloffm., non Parmelia, 

 Ach. ; Fries. Parmelia conoplea, Ach. Imbricaria, Dec. Pan- 

 naria, Delise. Parmelia rubiginosa, ^. conoplea, Fries, Lich. 

 Eur. 88 ; ^umma, i. 104. 



Exsic. Fries, Suec. 75. — Schser. Helv. 369. — Moug. et Nestl. 

 347. 



Hab. Trees in Stanstead Park, Essex, 1843, R. Jacobs. 



Though clearly shown and now universally considered to be 

 only a degenerated variety of P. rubiginosa (Squamaria affinis of 

 Hooker, Brit. FL, vol. v. p. 96), this Lichen [vide supra) was 

 treated as a distinct species by many of the older authors. " It 

 affects," says Schserer, " stones and the trunks of trees in shady 

 places in mountainous districts," and has been recorded from 

 Switzerland, France, Germany, and Sweden. 



2. Lecidea Candida (Lichen candidus, Weber, Spic. 193). 

 Thallus white on the upper surface, black beneath, composed of 

 short, tumid, tartareous scales, aggregated into a rugoso-plicate 

 crust, which is flattened at the circumference ; apothecia placed 

 at the edge of the scales, black, csesio-pruinose, white within, 

 margin thick, prominent, usually flexuose. — Lichen candidus, 

 Weber, Spic. 193, non FL Dan. t. 1064, fig. 1. Patellaria, 

 Hoffm. ; Sturm ; Psora, Dec. Lecidea, Ach. Meth. 79 [in part) ; 

 Lich. Univ. p. 212; Schcer. Spic. 120; Enum. Crit. 103; 

 Wahl Suec. 1717; Fries, Lich. Eur. 285, ececL syn. Eng. Bat. 

 1138; Summa, i. 112. 



Exsic. Ehrh. Cr. 49.— Schter. Helv. 167.— Moug. et Nestl. 

 642. 



Hab. Stanstead, Essex, 1843, R. Jacobs. 



This species is frequent in calcareous districts, either amongst 

 the mountains or plains throughout Southern and Central Eu- 

 rope, and extends as far north as Lapland and St. Petersburg. 

 It comes under the scope of Psora as described in the ' British 

 Flora,' and thus belongs to a group of species of the Friesian 

 genus Lecidea, of which L. vesicularis (Psora cseruleo-nigricans) 

 is the only other clearly established indigenous representative. 

 In appearance L. Candida considerably resembles that common 

 and very variable Lichen, but may be known by its closer and 

 pure white crust, and by its permanently pruinose apothecia. 



