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



are nearly obliterated and scarcely visible. Lam. prol. pale, more 

 or less tinged with brown. Sporidia as above, sometimes how- 

 ever one extremity is a little broader and more obtuse than the 

 other, and so of a subclavate fusiform shape ; in an old state 

 becoming of a brovv^n colour and more expanded in width, the 

 septa nearly or quite obliterated. The brown membranes of the 

 whole eight sporidia are constantly seen still enclosed in the 

 ascus, which is never observed in Chevallieri and rupestris. The 

 septa vary in number, sometimes five, six or seven, four on one 

 side and three on the other of the central cell, which is always 

 the largest. 



The specimen of 0. lithyrga from Schleicher in herb. Borrer. ! 

 is a very indifferent one, is on a quartzose rock and nearly or quite 

 denuded of the thallus, which is discoloured brown. The spo- 

 ridia decide its proper arrangement. 



The specimens from Ardingley are on coarse white sandstone, 

 quite destitute of thallus, the lirellse, which are crowded and 

 numerous, resting on the stone itself. 



Chevallier (/. c.) says, " sa croute est tant6t epaisse d'un beau 

 noir :" this state I have never seen. 



The specimen of O. saxicola, Ach., from Schleicher in herb. 

 Borrer. ! seems to be something in a young state. It is too im- 

 perfect to say positively to what it really belongs, but judging 

 from its general appearance, I incline to refer it to O. rupestris 

 rather than to O. saxatilis, DC, with which Mr. Borrer (E. Bot. 

 Suppl. /. c.) seems to consider it identical. 



The rigid lirellse, stellato-divei'gent, tapering towards either 

 extremity, and the form and septa of the sporidia are the cha- 

 rafcters which keep it distinct from Chevallieri and rupestris. 

 Plate V. fig. 3. a, Vertical section of thallus and lirella; b, sporidia. 



4. O, Chevallieri, Lirellse simple, linear, elongated, curved or 

 bent back, flexuose and wavy, black; sporidia eight in asci, 

 broadly clavate, rounded at each extremity, 3-septate, pale 

 yellow. 



Opegrapha lithyrga, Chev. Hist, des Graphidees, 54. t. 11. figs. 4 & 5 (excl. 



Ach. synon.) (1824). 

 saxatilis, Hook. Br. Fl. 2. 145 (in part) (1833); Tayl. Fl. Hib. pt.2. 



106 (in part). 



atra, e. lithyrga, Schrer. Enum. 154 (1851). 



Chevallieri, Leight. Lich. Brit.Exsic. 67! (1852). 



North Wales, Rev. Hugh Davies. Killarney (on the same stone 

 with O. saxatilis) ! Miss Hutchins. Netley Abbey ! Mr. Lyell. 

 Rocks on the sea-shore at Derriquin, Co. Kerry ! Dr. Taylor. 

 North of England ! Rev. J. Harrimann ; all in herb. Borrer. 

 Craigforda near Oswestiy, Shropshire ! Llanaber ! Barmouth ! 

 Rev. T. Salwey. Colin Glen, Belfast ! Mr. W. Thompson. Great 

 Orme's Head, Caernarvonshire! South Stacks, Holyhead ! Aber. ! 



