xylographa] geaphidace^ 223 



5. L. petraea Nyl. in Act. Soc. Linn. Bord. ser. 3, i. p. 393 

 (1856). — Thallus obsolete. Apothecia linear, simple, black, 

 slightly shining, gregarious, often somewhat flexuose ; margins 

 tumid ; disc narrow ; hypothecium thick, black ; paraphyses 

 very slender, somewhat branched ; ascus polyspored ; spores 

 very minute, 0,003-4 mm. long, 0,001 mm. thick ; hymenial 

 gelatine pale-bluish, then wine-red with iodine. — Oromb. Lich. 

 Brit. p. 95, Leight. Lich. Fl. p. 360 ; ed. 3, p. 393. Opegrapha 

 petraea Dur. Expl. Sci. Alger, p. 278 (1846) (excl. syn.) 

 (non Ach.). 



Exsicc. Larb. Csesar. n. 40. 



Not to be confounded with Lecanora simplex, to states of which 

 it bears considerable resemblance, but differs in the lirelliform, con- 

 gregate apothecia and the black hypothecium. The thallus is 

 indicated merely by a rudimentary dark hypotballus. 



Hab. On rocks, in maritune districts. — Distr. Pound only in the 

 Channel Islands and W. Ireland; no doubt to be detected elsewhere. 

 — -B. M. Le Fret, Noirmont and La Moye, Jersey ; near Kylemore and 

 Lettermore, Galway. 



86. XYLOGRAPHA Pr. Summa Veg. Scand. p. 372 (1849) 

 pro parte; Nyl. in Mem. Soc. Sci. Nat. Cherb. iii. p. 187 (1855). 

 {Stictis § Xylographa Fr. Syst. Myc. ii. p. 197 (1823) emend.) 

 (PI. 23.) 



Thallu^ developed under the bark (hypophloeodal). Algal 

 cells Palmella. Apothecia innate or erumpent, lirelliform, not 

 carbonaceous, roundish-oblong or irregular ; the disc plane or 

 concave ; hypothecium usually pale ; paraphyses slender ; spores 

 8 in the ascus, simple, colourless ; spermogones with simple 

 sterigmata and acicular curved spermatia. 



Differs from Lithographa in the plane or concave apothecia and 

 in the colourless or pale hypothecium. 



1. X. parallela Fr. Summa Veg. Scand. p. 372 (1849).— 

 Thallus forming elongate whitish spots or little visible 

 (K — , CaCl — ). Apothecia innate, erumpent, black, narrowly 

 linear, straight, developed in parallel rows, at first concave with 

 slightly elevated margin, becoming plane and immarginate ; 

 hypothecium colourless ; paraphyses discrete, brownish at the 

 apices; spores ellipsoid, 0,011-16 mm. long, 0,005-7 mm. thick; 

 hymenial gelatine bluish then violet-coloured with iodine. — 

 Oromb. Lich. Brit. p. 95 ; Leight. Lich. Fl. p. 362 ; ed. 3, p. 391. 

 Lichen parallelus Ach. Lich. Suec. Prodr. p. 23 (1798). Stictis 

 parallela Fr. Syst. Myc. ii. p. 197 (1822) ; Hook, in Sm. Engl. 

 Fl. V. 2, p. 213 (1836) ; Cooke Brit. Fung. p. 736 pro parte. 



Exsicc. Oromb. n. 96. 



Easily recognized by the peculiar arrangement of the fructification. 

 In the British specimens the thallus is but seldom distinct, being 



