Bev. W. Ar Leigliton on the British Graphideae. 205 



Owing to the great thickness of the substance of the lirella 

 compared with the small lamina proligera, the sporidia have been 

 seen with difficulty and with some uncertainty. They are veiy 

 minute, and as represented in 



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



10. Opegrapha herpetica, Ach. Thallus thin, subtartareous, 

 more or less cracked or slightly rugged, dusky olive, limited ; 

 lirellse small, innate, round, oval, oblong or linear-oblong, ob- 

 tuse, simple and divided, straight or curved ; disk rimseform, 

 expanded in age ; proper margins thick, rounded and inilexed ; 

 sporidia in asci, eight, fusiform, 3-septate, pale yellow. 



«. vera. Thallus tuberculate^ pulverulent ; lirellse imbedded, 

 small, simple, naked. 



Lichen herpeticus, Ach. Prodr. 20 (1798), sec. specim. ab Achario seipso ia 



herb. Borrer ! 

 Opegrapha herpetica, Ach. Meth. 23 (1803) ; Sm. E. Bot. t. 1789 ? ; Cheval. 



Graph. 82. t. 19. fig. 1. a. brunnea, 2, and f . linearis, 6 b; Heppe, Fl. 



Wurzburg. 73 (excellent) ; Fmgerh. Tent. Fl. Lich. Eiffl. 21 ; Fries, 



L. Ref. 368 (in part, excl. syn.); Tuckermann, Lich. N. Amer. 7^ Un 



part). 



herpetica *, Ach. L. Univ. 248 (1810) ; Syn. 72. 



herpetica, y.fiiscata, Schser. Enum. 156 (1850). 



rimalis, ^.fuscata, Ach. L. Univ. 261 (1810). 



ruhella, Sm. E. Bot. t. 2347 (good), excl. syn. (1811) ; Hook. Br. Fl. 



2. 144. excl. all the sj-n. (except E. Bot. 2347), which belong to our 



8. rubella. 



rufescens, Hook. Br. Fl. 2. 144. in part (excl. syn.). 



rufescens, y.fuscata, Schajr. Spic. 327 (1836). 



— — atra, j3. siderella. Fries, L. Ref. 368 (1831), apparently from the s\tio- 



nvms and specimen quoted, in part. 

 Graphis herpetica. Mart. Fl. Brasil. 1. 88 (1833). 



On oak, ash, and beech. Bradwell, Suflfolk ! Mr. Borrer. 

 Twycross, Leicestershire ! Rev. A. Bloxam. Lasswade ! and near 

 Dundee ! Br. Greville. Oxfordshire ! Mr. Baxter in herb. Dr. 

 Greville. Orton Wood near Twycross, Leicestershire ! Rev. 

 A. Bloxam. Chelmsford, Essex ! Mr. H. Piygnt. Charnwood 

 Forest ! Rev. A. Bloxam. Haughmond Hill, Shropshire ! 



Thallus thin, subtartareous, somewhat pulverulent, coarsely 

 cracked, of a dark dusky olive, forming irregular patches limited 

 by a thickened brown wavy line or margin. Lirella numerous, 

 congregated close together but distinct, not crowded, immersed, 

 and imbedded in the thallus, and only slightly raised, small but 

 very variable in size and shape, roundish, oval, oblong, linear- 

 oblong, obtuse at the extremities, simple, straight, sometimes 

 slightly curved. Proper margins thick, rounded and inflexed, 

 encompassing a narrow rimseform disk, which however varies in 



