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



subradiate shapes ; disk black, plane, cracked ; sporidia in asci, 

 eight, broadly obovate, 3-septate. 



Arthonia Swartziana, Ach. Schrad. Journ. Bot. 1. 3. p. 13. t. 4. f. 1 (1806) ; 



Sm. E. Bot. 2079; Ach. L. Univ. 142; «. Syn. 6; Mart. Fl. Erlang. 



285 ; Fingerh. Fl. Eiffl. 25 ; Johnst. I Fl. Berw. 101 ; Hook. Br. Fl. 2. 



143; Tayl. Fl. Hib. pt. 2. 104 ; Leight. Lich. Brit. Exsic. 70 ! 

 Arthonia vulgaris, /3. Swartziana, Schajr. Spicil. 246 (1823-1836). 

 Opegrapha atra, X. Swartziana, Schaer. Spicil. 326 ; Exsic. 462 ! ; Enum, 



155. 



atra, y. macularis, Tuckerm. N. Amer. Lich. "15 (1848). 



Arthonia microscopica, /3. arthograpta, Wallr. Crj'pt. Germ. 322 (1831). 



On ash, near the Retreat, Berwickshire ! Dr. G. Johnston. On 

 smooth bark of trees. Shropshire, generally ! 



Thailus forming small subdeterminate patches, of an irregular 

 round or oblong shape, pale yellow or cream-colour with a tinge 

 of ashy-gray, or altogether ashy-gray, thin and scaling off here 

 and there. Ardellce numerous, closely approximate, of a very 

 irregular shape, with a substellate or radiate outline, arising as 

 it were from the apparent confluence of many ardellse into one 

 dark blotch of a full dull black colour. Disk flat or convex, 

 cracked irregularly. Sporidia of a very broad obovate form, 

 3-septate, pale yellow, eight in each ascus. 



Plate VIII. fig. 33. Opegrapha atra, X. Swartziana, Schser. Exs. 462 : 

 a, vertical section of ardella and thailus ; b, sporidia. — Shropshire 

 specimens of Arthonia Swartziana, Ach. : a , vertical section of 

 thailus and ardella ; b', sporidia. 



5. Arthonia impolita, Borr. Thailus thin, subtartareous, 

 cracked, indeterminate ; ardellse immersed, roundish or irre- 

 gularly oblong ; disk flat or slightly convex, brownish or lead- 

 coloured, rough, pruinose ; sporidia in asci, eight, obovato-linear, 

 rounded at the extremities, 3-, 4- or 5-septate. 



Verrucaria impolita, Hoffm. Fl. Germ. 2. 172 (fide Ach.). 



Lichen impolitvs, Ehrh. Crypt. 274 (fide Ach. et Schser.). 



Patellaria pruinata, Pers. in Ust. Ann. st. 7- p- 28 (1794). 



Lichen pruinatvs, Pers. in Ust. Ann. st. 1 1. p. 19 (1797). 



Parmelia impolita, Ach. Meth. 160 (1803). 



Arthonia pruinosa, Ach. L. Univ. 147. t. 1. f. 3 (1810); Syn. 7; Wallr. 



Crypt. Germ. 321 ; Moug. & Nestl. Stirpes, 1159 ! 

 Arthonia impolita, Borr. in E. Bot. Suppl. 2692. fig. 1 (1831); Hook. Br. 



Fl. 2. 143 ; Tayl. Fl. Hib. pt. 2. 104 ; Schsr. Enum. 242 ; Exsic. 506 ! ; 



Leight. Lich. Brit. Exsic. 131 ! 

 Parmelia impolita b*, Fries, L. Reform. 183 (1831 ). 

 Lecanactis impolita. Fries, Summa Veg. Scand. 118 (1846); Tuckerm. N. 



Amer. Lich. 77- 



On ivy. Kenilworth Castle, Warwickshire ! On oak. Hen- 

 field, Sussex ! On worked timber, Livermore, Suffolk ! all in 

 herb. Boner. Oswestry, Shropshire ! Rev. T. Salwey. On oak. 



