388 Rev. W. A. Lcighton on the British Graphidese, 



branched in a distinct and very elegant pedato-radiate manner, 

 wavy, curved and iiexuose, the extremities very acute^ immersed 

 and sunk. Disk broad_, plane or concave, clothed with a grey 

 pruina, the proper margin very thin and delicate, scarcely dis- 

 cernible, flanked by the raised, prominent, broken, rugose thal- 

 lodal margins. A vertical section shows that the ascigerous disk 

 is contained in a very thin brown membranous perithccium, 

 which entirely subtends the base, and forms one of the charac- 

 teristic distinctions between this and Chiographa and Graphis 

 Smithii [0, script a, E. Bot.). 



Specimens of this in herb. Borrer ! named Opeg. dendritica 

 by Acharius himself are identical with the E. Bot. figure, though 

 the figures and descriptions in the works of Acharius agree 

 better with our var. 7. obtusa. 



^. acuta. Lirellse ramifying at a very acute angle, neai'ly 

 parallel, extremities simple, acuminate; thallodal margin pro- 

 minent. 



On beech. St. Leonardos Forest, Sussex ! Mr. Borrer. Upton, 

 Pembrokeshire ! Rev. T. Salwey. 



7. obtusa. Lirellse ramifying at an obtuse angle in a furcate 

 manner, extremities very obtuse, frequently furcate; thallodal 

 margin nearly obliterated. 



On beech. St. Leonard's Forest, Sussex ! Mr. Borrer. Tun- 

 bridge Wells ! Mr. W. Thompson. Pembrokeshire I Rev. T, 

 Salwey. Castle Bernard Park, Bandon, Ireland ! Mr. I. Carroll. 



Plate VII. fig. 23. a. Vertical section of thallus and lirella; 6, sporidium. 



4. Chiographa. 



Apothecium lirellseform or subdisciform, sessile ; perithecium 

 carbonaceous, entire or surrounding the sides and base; disk 

 plane, broad, surrounded with a proper margin and an accessory 

 thallodal margin. Thallus membranaceous. 



Name from %tft)v, snow, and 'ypa<j)'rj, writing, in allusion to 

 the white powdery thallodal margin. 



1. Chiographa Lyellii. Thallus membranous, smooth and 

 waxy, determinate ; lirellse prominent, sessile, oblong or linear- 

 oblong, simple, curved ; proper margin narrow, prominent ; thal- 

 lodal margin elevated, white, pulverulent; disk plane, broad, 

 pruinose; sporidia in asci, eight, linear, margined, rounded at 

 the ends, containing about 7-8 transversely oval margined spores. 



Opegrapha Lyellii, Sm. E. Bot. 1876 (good) (1808) ; Fries, L. Ref. 373 

 (excl. E. Bot. 1813); Hook. Br. Fl. 2. 147 (excl. E. Bot. 1813); Schser. 

 Spic. 323 ; Enura. 152. 



Graphis Lyellii, Ach. Syn. 85 (1814). 



