96 Rev. W. A. Leighton on the British Graphidese. 



Thallus eflfase, thin, pulverulent, white. Lirellee numerous, 

 scattered or congregated close together, prominent and sessile, 

 black, elongated, narrow, wider in the centre, acuminated at both 

 extremities, for the most part simple, but frequently by juxta- 

 position becoming of a stellate arrangement, straightish or va- 

 riously curved and flexuose, usually with other lirelljje of a smaller 

 size, and either rotund or oblong, interspersed among them. 

 Proper margins narrow, elevated and prominent, wavy, flexuose 

 and inflexed. Disk broad, expanded, open and plane, without 

 pruina. 



To be distinguished from O. saxatilis by its place of growth 

 and the different form of the sporidia, 



Plate V. fig. .9. Sporidia. 



S. tigrina, Ach. Lirellse linear-oblong, obtuse at the extre- 

 mities ; disk channelled, nearly uniform ; proper margins per- 

 sistent, rounded and inflexed. 



Opegrapha signata, /3. tigrina, Ach. L. Univ. 262 (1810). 



diaphora (excl. syn.), Sm. E. Bot. t. 2280 (1811). 



notha, €. tigrina, Ach. Syn. 77 (1814), sec. specim. a Schleichero in 



herb. Borrer. ! 

 — "—versiftyrmiSi Chevalher, Graphid* p. 13. t. 1. f. 1 a (1824). 



varia, rj. tigrina, Scheer. Enum. 157 (1850). 



" ' varia, Pers." Bohler's Lich. Brit. no. 62! 



On beech, oak, elm. New Forest, Hants ! Mr. Lyell in herb* 

 Borrer, Hurst Pierpoint, Sussex ! Haddisco, Norfolk I Coulsdon, 

 Surrey ! Mr. Borrer. 



Thallus effuse, thin, pulverulent, dirty-white, often scarcely 

 visible. Lirellee numerous, scattered here and there, or crowded 

 in groups, prominent and sessile, for the most part simple, 

 straight or sometimes more or less curved, black, shining, linear- 

 oblong, narrow and nearly of the same width throughout, obtuse 

 and rounded at the extremities. Proper margins very thick, 

 prominent, rounded and inflexed, entire and uniform, not wavy 

 or crisped. Disk narrow, canaliculate, of about the same width 

 throughout and concave, sometimes a little dilated about the 

 middle and then plane. 



Plate V. fig. 9. Sporidia. 



€. tridensj Ach. Lirellse elongated, stellately arranged ; disk 

 channelled ; proper margins persistent, rounded and inflexed. 



Opegrapha tridens a, Ach. L. Univ. 263 (1810); Syn. 79. 



varia, d. diaphora. Fries, L. Ref. 365. in part (1831). 



varia, Hook. Br. Fl. 2. 145. in part (1836). 



varia, t. tridens, Schscr. Enum. 158 (1850). 



On beech and elm. New Forest, Hants ! Mr. Lyell in herb, 

 Borrer. Sussex ! Mr. Borrer. 



