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 ct. Sf /3, Ach. L. Univ. 256 ? 



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



rufescens, /3. siderella, Sch^rer, Spicil. 50. 327 (1823-1836) ; Enum. 



155; Exsicc. 96! 

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



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

 atra, (3. 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. Proper 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 different from the siderella of Acharius, 

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

 Opegrapha Schcereri, 



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

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



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



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

 verulent, cracked, pale yellowish gray, effuse; lirellse 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 ! Hunston churchyard ! and 

 Aldingbourne churchyard ! Sussex, Mr. Borrer. 



Thallus effuse, very thin, tartareous, somewhat pulverulent. 



