94 Rev. W. A. Leighton o» the British Graphideae. 



** Corticola. 



7. 0. varia, Pers. Thallus pulverulent, white ; lirellse promi- 

 nent, sessile, round, oblong, elliptical or elongated and attenu- 

 ated at each end ; disk canaliculate or dilated in the middle, or 

 plane and convex; proper margins prominent, inflexed, some- 

 times subevanescent ; sporidia in asci eight, irregularly obovate 

 or obovate-fusiform, 5 -septate, the central cell larger, hyaline, 

 pale yellow. 



The so-called varieties of this very variable lichen seem to be 

 more properly speaking states, arising from a greater or lesser 

 development of the lirellse dependent upon local circumstances, 

 localities or atmospheric influences, or of more or less mature 

 age. The sporidia are alike in all. 



a. pulicaris, Lightf. Lirellae oval, oblong or elliptical, mi- 

 nute, simple ; disk concave, dilated in the middle ; proper mar- 

 gins persistent, inflexed. 



Ldchen crustaceus, Sfc, Mich. Gen. PL p. 102. t. 54. ord, 37. f. 2? (1729). 



scriptus, ^. pulicaris, Lightf. Fl. Scot. 2. 801 (1777). 



pulicaris, Hoffm. En. 14. t. 3. f. 2.js? (1784). 



Verrucaria pulicaris, Willd. Fl. Berol. 370 (1787). 



Lichen vulvella, Ach. Prodr. 22 (1798). 



Opegrapha vulvella, Ach. Meth. 19. 1. 1. f. 9 (1803); Wahl. Fl. Suec. 859. 



vulvella, X. Sj- ^. pulicaris, Ach. L. Univ. 251 (1810). 



vulvella at., Ach. Syn. 77 (1814). 



notha, Mart. Fl. Erlang. 278. in part (1817). 



cymhiformis, a. pulicaris fy /3. phcea, Schaer. Spied. 50. 329 (1823- 



1836); Exs. 971518! 520! 



cymbiformis, Heppe, Fl. Wui'zburg. 75 (1824); Fingerhuth, Eiffl. 24. 



ramealis, Chevalher, Graphid. 65. t. 14. f. 3 (1824). 



stizorina, Chevallier, Graphid. 66. t. 14. f. 4 (18- i). 



Graphis pulicaris, Wallr. Crypt. Germ. 335 (1831). 



Opegrapha varia, a. pulicaris. Fries, L. Ref. 364 (1831) ; Hook. Br. Fl. 2. 



145. in part. 



varia, a. pulicaris, Tuckermann, N. Lich. 75. 



varia, y. pulicaris 8f ^. phcea, Schser. Enum. 156. 



On beech and ash. Sussex ! Mr. Borrer. New Forest, Hants ! 

 Mr. Lyell in herb. Borrer. 



Thallus effuse, thin, pulverulent, whitish, almost obliterated. 

 LirellcE numerous, scattered, prominent and sessile, minute, tu- 

 mid, either oval, oblong, elliptical or elliptico-oblong, sometimes 

 a little elongated, straight, sometimes curved, generally simple, 

 occasionally triquetrous, obtuse at the extremities, dark brown- 

 black, broad for the size, but variable in width, according to the 

 greater or lesser degree of expansion of the disk, which is either 

 regularly canaliculate and of the same width throughout, or 

 more or less dilated, frequently very considerably in the middle. 



