Rev. W. A. Leighton on the British Graphideae. 209 



ingly similar in appearance to those of Opeg. Chevallieri. Disk 

 in a perfect state a mere chink, uniform in width throughout, in 

 an older state becoming wider, more open and expanded. Proper 

 margins very round, tliick, plump and intiexed. 



Plate V. iig. 13. a. Vertical section of thallus and lirellae; b, sporidia. 



/8. stenocarpa. Lirellae long, slender and wavy, densely 

 crowded ; disk rimseform, very narrow, closed. 



Opegrapha stenocarpa a, Ach. L. Univ. 25" (1810); Sj-n. 75; Chevallier, 



Graphid. 37. t. 7. f. 5 c; Heppe, Fl. Wurzburg. 7 A; Fingerh. Fl. 



Eiffl. 23. 

 atra, /3. stenocarpa, Schaer. Spicil. 48. 324 (1823-1836) ; Enum. 153 ; 



Exsicc. 93 ! (in part) ; Fries, L. Ref. 367; Siunma V. S. 118; Tucker- 



mann, North. Lich. "J^. 



atra, y. gyrograpta, Wallr. Crv'pt. Germ. 326 (1831). 



rimicola, Clieval. Graphid. 41^ t. 9. f. 1 (1824). 



Graphis stenocarpa, Meyer in Spreng. Syst. Veg. 4. 1. 250 (1827). 



On oak, beech, elm. Sussex ! Mr. Borrer. New Forest, 

 Hants ! Mr. Lyell in hei-b. Borrer. Lasswade ! Dr. Greville. 

 Twycross, Leicestershire ! Rev. A. Bloxam. Near Cork, Ire- 

 land ! Mr. I. Carroll. Near Shrewsbury ! Gloddaeth, Caernar- 

 vonshire ! 



Thallus effuse, thin, membranous, somewhat scaly or scurfy, 

 continuous, pale dirty yellow, scarcely if at all cracked, though 

 in old specimens very considerably cracked, and of a scurfy pul- 

 vei-ulent appearance. Lirellae very numerous and crowded, never- 

 theless quite distinct, forming a sort of black nethke work over 

 the thallus, sessile, promment, variable in size, the smaller ones 

 short and oblong, the larger ones more considerable in number 

 and frequently no others are present, very long and slender, nar- 

 row, linear, curved, flexuose, and wavy in all degrees and direc- 

 tions, of nearly the same width throughout but narrower at the 

 extremities, of a full black, more or less shining, often with a 

 greasy aspect. Disk a very narrow chink of the same uniform 

 width throughout, even in old age when it becomes a Httle more 

 open. Proper margins veiy thick in proportion to the disk, 

 rounded, prominent, and inflexed. 



There are specimens in which the transition between the va- 

 rieties vulgata and stenocarpa are clearly traceable. 



Plate V. fig. 13. a 1, Vertical section of thallus and lirellae ; b, sporidia. 



12. Opegrapha siderella, Ach. ? Thallus thin, subtartareous, 

 cracked, pale dusky yellow, limited ; lirellre small, innate, various 

 in size, rounded, oblong or linear, straight or curved, chiefly 

 simple ; disk rimaeform, uniform ; proper margins rounded and 



Ann. i^ Mag. N. Hist. Ser. 2. TW. xiii. " 14 



