Rev. W. A. Leighton on the British Graphideae. 83 



tends our knowledge of species by describing and figm-ing with 

 his characteristic perspicuity and acuteness many additional ones. 

 He also invented the expressive term lirella for the apothecium. 

 DeCandolle (Flor. Franyaise, 1803) comprehends Opegrapha in 

 the 2nd Tribe, Pseudo- Lichenes, of his Order Hijpoxyla, inter- 

 mediate between Fungi and Lichenes, and comprising in the 

 IstTi'ibe (Pseudo-Fungi) the geneva, Rhizomorpha, Sphceria, Nee- 

 maspora, Xyloma and Hypoderma ; and in the 2nd Tribe, Hyste- 

 rium, Opegrapha^ Ven'ucaria and Pertusaria. Acharius in his 

 'Lich. Univ/ (1810) distributes the comprehensive genus Ope- 

 grapha of previous authors into three separate genera, distin- 

 guished by the structure of the apothecium, viz. Arthonia, Ope- 

 grapha and Graphis. The first is characterized by an apothecium 

 subrotund, plane, without a proper margin and covered with a 

 black membrane ; the second by an apothecium elongated, having 

 a proper margin, perithecium entire and suiTOunding the base 

 and sides, sessile and without a thallodal margin ; and the third 

 by an elongated apothecium, with a proper margin, perithecium 

 lateral only, the base being naked, immersed, and with a thal- 

 lodal margin. The name Graphis, though adopted from xVdan- 

 8on and Ehrhart, was not used by him in the comprehensive 

 sense of these authors. The same arrangement, with some modi- 

 fications and numerous additions to the species, was continued 

 by Acharius in his * Synopsis ' (1814). Dufour published a Mo- 

 nograph of this tribe in the * Jom-nal de Physique ' for 1818, and 

 Chevallier in the same journal for February 1822 published a 

 precis of his proposed larger work. The latter in his unfinished 

 ^Histoire des Graphidees^ (1824) forms a new order termed 

 Pheropliorece, equivalent to the 2nd Tribe, Pseudo-Lichenes, of 

 DeCandolle^s Hypoxyla, and divides it into two tribes : — 1st, 

 Graphideae, containing Opegrapha, Allographa, Arthonia and 

 Schizoxylon ; 2nd, VeiTucarioidece, containing Verrucaria, Pyre- 

 nula, Trypethelium, Glyphis and Chidothecia. Opegrapha is di- 

 vided into two sections, Hysterina= Opegrapha, Ach., and Gra- 

 phina= Graphis, Ach. Allographa is made up of exotic species, 

 and is founded on Graphis Poitai, Fee, and Graphis Afzelii, Ach. 

 [?if therefore equivalent to Fries's Graphis, S. 0. V.]. Arthonia 

 =^ Arthonia, Ach.; Schizoxylon, Pers. and Auct., according to 

 Fries (S. O. V. 121) a genus of Fungi of his Order Xylomacei. 

 The published portion of the work comprises only the first and a 

 small part of the second subdivision of the section Hystei'ina of 

 Opegrapha, and is illustrated with twenty coloured plates fiUed 

 with representations, nat. size and magnified, many of them 

 veiy faithful, and characteristic of the various forms rather than 

 distinct species with which the author would bring us acquainted. 

 Schserer in his 'Spicilegium' (1823-1836), and in his other 



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