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



between tlie three tribes. The GrapMdece are most abundant in 

 the tropics, the genera decreasing northwards, some few obsolete 

 vestiges of tropical genera remaining in Southern Europe. The 

 species also decrease in similar geographical mode, one only, 

 Arthonia radiata, being found in Lapland. This geographical 

 distribution he regards as of the highest importance both in 

 distinguishing the species and determining abortive forms. Con- 

 cerning few tribes has greater diversity of opinion prevailed (and 

 it still prevails) as to what genera should or should not be in- 

 cluded in it, and of course it has been subjected to numberless 

 modifications and frequent changes of arrangement. The fol- 

 lowing succinct summary will show the history of the tribe so 

 far as it could be gained from the works within our reach. 



Ray, in the 3rd edition of his ' Synopsis/ p. 71. n. 48 (1724), 

 mentions a lichen " peregrinis velut Uteris inscripta," which both 

 Micheli and Dillenius identify with their plants. Micheli (Nova 

 Genera, 1729) represents in tab. 56. f. 3, an Opegrapha growing 

 on the hazel, which Fries (L. Reform. 463) refers to Opegrapha 

 stenocarpa, Ach. He describes (p. 102) also two other forms, 

 one growing on holly in England, and the other (which Dillenius 

 considers as a variety only of the former) on hazel. He includes 

 them in his Ordo 37, which is a singular conglomeration of 

 heterogeneous plants, Lichens and Fungi. Dillenius (Muse, 

 p. 125, 1741) regards the figure of Micheli (t. 56. f. 3) as iden- 

 tical with his own figure in tab. 18. fig. 1. A & B, representing 

 a plant occurring on the oak and elm. They appear to me very 

 dissimilar in appearance. Fries (L. Reform. 370 & 463) refers 

 Dillenius's figure to Graphis scripta, Ach. Most probably both 

 these elder writers intended to comprehend all Opegraphce gene- 

 rally under their descriptions and figures, not having devoted 

 themselves to distinguish the various species. Adanson in ^ Fa- 

 milies des Plantes' (1763) first allotted a particular name to 

 these plants, Graphis, which Ehrhart also adopted in his ' Plantae 

 Exsiccatse.^ Linnaeus in his ' Sy sterna Vegetab ilium ' (1767) and 

 all his subsequent writings included them all under his Lichen 

 scriptus. And this view was followed by all subsequent authors 

 until Humboldt (Flor. Friberg. 1793) first published the genua 

 Opegrapha, constituted originally (see Luyken, Tentam. 44, and 

 Humb. Fl. Frib. 57) by Willdenow [?in MS., certainly not in 

 his Prodr. Fl. Berol.], under which he arranges three species 

 which had been previously described by preceding writers under 

 another name, Veirucaria. The name Opegrapha vf as adopted 

 by Persoon, Schrader (Spicil. Fl. Germ. 1794), Acharius (Prodr. 

 1798&Meth. 1803), Lamarck and DeCandolle (Flor. Fran9aise, 

 1803), Dufour and other botanists xmiversally. Persoon in 

 ^Usteri Annal.' st. 7 (1794) and in the 'Act. Wetter.' first exr 



