148 LICHENES. [Verrucaria. 



yet, well marked as it appears to be, Mr. Borrer observes that there are 

 varieties most puzzlingly intermediate between it and O. Lyellii. 



16. O. venosa, Pers. (veiny Opegrapha); crust tartareous de- 

 terminate reddish- white, apothecia immersed convex without any 

 proper border repeatedly branched curved parallel and equidis- 

 tant obtuse at the ends, surrounded by a slightly elevated acces- 

 sory border formed of the crust. Pers. in Annul der Wetterav. 

 v. 2. p. 15. t. 10./. 2. E. Bot. t. 2454. 



On the trunks of Beech in the New Forest, Hampshire, and almost 

 always surrounded by Pertusaria crassa, C. Lyell, Esq. — Sir Jas. E. Smith 

 well describes " the lirellce as curiously and regularly disposed, much 

 branched, twisted; but their ramifications, however complex and varied, 

 keep generally at equal distances from each other, like the walls of an 

 artificial maze. They are deep sunk in the crust, but convex above, in- 

 tensely black with obtuse terminations; not tapering to a point, as in O. 

 dendritica, nor do they, as in that, spread radiating from a centre." Mr. 

 Borrer, in a letter, doubts the correctness of the reference to Persoon : 

 but although it must be confessed that his short description is very un- 

 satisfactory, the figure seems to be sufficiently characteristic. The same 

 acute observer has already, in E. Bot. Suppl., under Arthonia impolita (/. 

 2692), remarked that " Meyer has perhaps done well in placing O. den- 

 dritica and O. Lyellii in a new Genus, his Platygramme, to which our 

 O. venosa also must belong. They appear to differ from Opegrapha by 

 wanting a proper border to the apothecia and they can scarcely be 

 placed in Arthonia:' Most of the species referred to Platygramme by 

 Sprengel are exotic, natives of China. Our own 3 species appear to 

 prefer the warmer parts of Europe, and in Britain they inhabit the 

 southern districts only. 



Obs. The Opegrapha macularis of Ach. and O. epiphaga of Ach. and E. 

 Bot., are altogether to be excluded from the Lichens, as species of Hy- 

 sterium.(Borr.) M. Fee, however, still ranks them among the Lichens, and 

 in the present family, forming of them a Genus which he calls Hctero- 

 grapha. 



b. Apothecia hemispherical (tubercula), enclosing a nucleus. 

 Fam. IV. Verrucarieje. 



5. Verrucaria. Pers. Verrucaria. 



Thallus crustaceous or cartilagineo-membranaceous, spread- 

 ing-, adnate, uniform. Apothecia (tubercula) hemisphaerical or 

 subglobose, innate and immersed or sessile, corneous, of a dif- 

 ferent colour and substance from the thallus, (mostly a black 

 crust or shell) enclosing a nucleus, the apex papillary, often at 

 length perforated, sometimes covered by the wart-like processes 

 of the thallus, (when it constitutes the Pyrenula, Ach.) — Name: 

 verruca, a wart, from the wart-like processes on the thallus. 

 — The characters of this genus are not satisfactorily defined. 

 Pyrenula, separated from it by Acharius, is, by almost general 



