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



its expansion, apparently according to age. Sporidia the same 

 in all the varieties, eight in asci, fusiform, 3-septate, pale yellow, 

 easily separable from the ascus, straight when seen on their back 

 or front, curved when lying on their sides. Fries's remark {l. c.) 

 respecting the thallus is admirably characteristic : " Crusta vera 

 sub epidermide latens albissima, mox vero in verrucis granulosis 

 albis erumpentibus colleeta, unde crusta extus albo-guttata. In 

 minus evolutis speciminibus tamen laevigata est.^^ According to 

 the specimens in herb. Borrer ! ! ! '^ Op. rubella and rufescensj 

 Brit. Fl." are confounded together, and are distributed into this 

 and the following varieties. The sporidia in Schserer's Opeg. her- 

 petica, oL. rubella, Enum. 155, Exs. 95 ! and S. subocellata, Exs. 

 281 ! are identical with those of our plants ; but his var, /3. side- 

 rellaj Exs. 96 ! is a distinct species having sporidia elongato- 

 fusiform, 13-septate. 



Plate V. fig. 12. a. Vertical section of thallus and lirella; b, sporidia — all 

 magnified. 



P, subocellata, Ach. Thallus tuberculate, pulverulent ; lirellse 

 imbedded, ocellate. 



Opegrapha siderella, iS. cenea, Ach. Meth. 26 (1803), sec specim. ab Achario 



seipso in herb. Borrer ! 



rubella, 8. cenea, Ach. L. Univ. 250 (1810). 



rubella, e. subocellata, Ach. L. Univ. 250 (1810). 



herpetica, y. subocellata, A.ch. Syn. 73 (1814). 



subocellata, Heppe, Fl. Wurzburg. 73 (1814) (excellent) ; Fingerh. 



Tent. Fl. Lich. Eiffl. 22 (1829). 

 herpetica, Fries, L. Reform. 3G8. in part (1831); Tuckermann, N. 



Amer. Lich. 75 (in part). 



a. simplex. Lirellse small, simple. Opegrapha subocellata, 

 7. (2nea, Cheval. Hist. Graphid. 82. t. 19. f. 4, as to colour and 

 general appearance ; a. brunnea, fig. 1 a, as to detail. 



On ash and willow trees. Hurst, Cuckfield and Ardingley, 

 Sussex ! Mr. Borrer. Bo vingar, Essex ! Mr. Lyell in herb. Borrer. 

 Near Thirsk, Yorkshire ! Mr. J. G. Baker. 



Thallus thin, subtartareous, somewhat pulverulent, continuous, 

 scarcely if at all cracked, rough or rugose, with innumerable 

 minute raised irregularly-shaped pale-coloured or whitish eleva- 

 tions or projections, pale dirty tawny olive, raised around the 

 lirellse into a sort of spurious thallodal margin, narrow, whitish 

 and pulverulent, forming extensive patches either limited by a 

 brown wavy margin, or diffuse and without such being visible. 

 I^irellm simple, of the same size, shape and number, and im- 

 mersed, as in the last. 



b. divisa. Lirellse larger, substellate. Opegrap)ha subocellata, 

 ^. grisea, Cheval. Hist. Graphid. 82. t. 19. f. 3. 



On ash trees. Hurst, Sussex ! Mr. Borrer, 



