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



inflexed ; sporidia in asci, eight, elongato-fusiform or aciculate, 

 13-septate, pale yellow. 



Lichen siderellus, Ach. Prod. 24? excl. syn. (1798). 

 Opegrapha siderella, Ach. Meth. 25? (1803) ; Syn. 79? 



siderella a,. ^ ^, Acli. L. Univ. 256 ? 



— — rubella, Moug. & Nestl. Stirpes, 648 ! (1820). 



rufescens, (i. siderella, Schserer, Spicil. 50. 327 (1823-1836) ; Enum. 



155; Exsicc. 96! 

 rufescens, Hook. Br. Fl. 2. 144 (excl. syn. O. phcea and 0, herpetica, 



and E. Bot.) in part (1833). 

 atra, j3. siderella, Fries, L. Reform. 368. in part (1836). 



On beech in New Forest, Hants ! Mr. Lyell in herb. Borrer (a 

 single specimen). 



Thallus thin, subtartareous, cracked, somewhat pulverulent 

 and leprose, forming irregular patches of greater or smaller ex- 

 tent, with a wavy margin but not bounded by any line, of a pale 

 dusky dirty yellow. Lirellce numerous, pretty regularly scat- 

 tered over the whole thallus, minute, innate or immersed at the 

 base, the upper half only prominent, very various in size, punc- 

 tiform, rounded, subtriquetrous, oblong or linear, straight or 

 crowded, simple or sometimes with a short branch, very plump 

 in general appearance and obtuse at the extremities, dull black, 

 somewhat greasy-looking, Froper margins rounded and inflexed. 

 Disk a mere chink, uniform in width throughout or more open 

 in age. 



Our plant and Schserer's are identical, but T doubt whether 

 they be the same as Acharius's plant, judging from the descrip- 

 tion, which states the lirellse to be stellate, and also from his re- 

 ference to Persoon^s figure, and it is almost impossible to decide 

 without comparison with an authentic Acharian specimen. If it 

 should prove to be really diflerent from the siderella of Acharius, 

 then it is a " nova species,^' and will appropriately be named 

 Opegrapha Schcei-eri. 



The appearance of this plant at first sight is a good deal like 

 that of O. heipetica, but the sporidia keep them distinct. 



Plate VI. fig. 14. a. Vertical section of thallus and lirella; h, sporidium. 



13. Opegrapha taxicold. Thallus very thin, tartareous, pul- 

 Terulent, cracked, pale yellowish gray, effuse; lirellaj large, ex- 

 cessively prominent and sessile, oblong, linear or linear-elongate, 

 straight or curved, chiefly simple ; disk broadly rimseform ; pro- 

 per margins rounded and inflexed, rugged ; sporidia in asci, 

 eight, elongato-fusiform or acicular, 13-septate, pale yellow. 



On yew. Funtington churchyard ! Ilunston churchyard ! and 

 Aldingbourne churchyard ! Sussex, Mr. Borrer. 



Thallus effuse, very thin, tartareous, somewhat pulverulent. 



