Collema.] LICHENES. 107 



Ach. Meth. p. 31 . Gr aphis dendritica, Ach. L.U.p.27]. Eng. 

 Bot. t. 1756. p. rupestris. Tliallus thin, olive-coloured, pru- 

 inose, thallodal margin of the lirellce white ; apothecia minute, 

 elongated, branched. 



. on trees common. . on siliceous rocks, at Carig Mountain, 

 County of Kerry. 



8. O. sulcata, PERS. Thallus membranaceous, subtartareous, 

 subrugose, subdeterminate, of a brownish-grey ; apothecia black, 

 large, emerging, at length prominent, tumid, the disk narrow, 

 the border tumid, with two or three longitudinal grooves, each 

 surmounted by a film of the thallus. Persoon MSS. according 

 to Mugeot and Nestler, in Cr. Vog. Rhen. No. 360. 



On holly ; near Belfast, Mr. Templeton. Killarney woods, com- 

 mon. Thallus from three to four inches wide, closely investing the 

 bark near the border, where, on meeting other lichens, it throws up a 

 black edge ; sometimes the thallus is cracked, and always uneven, with 

 minute elevations or wrinkles. Apothecia larger than in any other 

 British species, mostly simple, though often much bent, raising up a 

 film of the thallus on each side as they emerge ; the disk narrow, the 

 border thick, tumid, and having two, three, and, more rarely, four 

 grooves on each side ; the tops of the ridges displaying each a longi- 

 tudinal scale from the thallus. The lamina proligera has a black disk, 

 but is itself gelatinous, pale, semitransparent when wet, striated with 

 erect linear cellules. This species is allied by the thallus to O. elegans 

 of Smith : the structure of the lirellce, however, is very distinct. 



* * * Apothecia discoid, round, sessile, or emerging. 

 f Thallus (in a moist state} gelatinous. 



20. COLLEMA, Ach. 



Thallus homogeneous, gelatinous when wet, when dry, hard and 

 cartilaginous, sometimes foliaceous. Apothecia orbiculate, 

 (rarely on podetia), bordered, formed entirely of the thallus. 



* Thallus somewhat crustaceous. 



1. C. nigrum, ACH. Thallus crustaceous, sooty black, crack- 

 ed, with minute, imbricated, inciso-crenate lobes, the border 

 bluish ; apothecia scattered, minute, black, at length convex, 

 and their border evanescent. Ach. L. U. p. 628. Eng. Bot. t. 

 1161. 



On limestone ; common : on sandstone, near Belfast, Mr. Tem- 

 pleton. 



* * Thallus broadly lobed over the whole surface, imbricated, plaited, 

 spreading, very turgid when wet. 



2. C. fragans, ACH. Thallus suborbicular, olive black, the 

 lobes ascending, crowded, somewhat round, thick-edged, ere- 



