Rev. W. A. Leighton on the British Graphidese. 391 



With a single furrow the plant is as represented in E. Bot. 

 t. 1812, with many furrows it becomes Op. sulcata, Pers., Tayl. 

 Fl. Hib. 107, but as these variations with every intermediate 

 gradation are all clearly traceable abundantly on almost any patch 

 of considerable size, they seem to be too inconstant to constitute 

 distinct varieties, evidently being only different states. The 

 singular structure of the perithecium when seen in a vertical 

 section will be sufficiently intelligible by reference to our PL VII. 

 fig. 26 «,« 1. The sporidia are very large and peculiar, of a linear- 

 elongate form, slender and narrow, consisting of about 11-13 

 transversely oval pale yellow spores with white margins, con- 

 nected together, the central one the largest, the others gradually 

 diminishing in size towards each extremity, the whole invested 

 with a thin hyaline membranous sac, which under the micro- 

 scope appears to form a broad white articulated border to the 

 sporidium. 



Plate VII. fig. 26. a. Vertical section of lirella with a single furrow on 

 the proper margins; a 1, vertical section of lirellae with many 

 furrows on the proper margins ; b, sporidium. 



6. Lecanactisj Eschw. 



Apothecium lirellseform, or subdisciform, immersed; perithe- 

 cium carbonaceous, entire or surrounding the sides and base ; 

 disk plane, open, pruinose, surrounded with a proper margin. 

 Thallus crustaceous. 



Name from XeKcivrj, a dish, and d/crlv, a ray, probably from its 

 affinity to the genus Lecidea, whose apothecia are patellulce. 



The structure of the perithecium would have led me to arrange 

 this with the genus Opegrapha, but it is retained in deference to 

 the authority of Eschweiler and Fries, the latter of whom, speaking 

 of its affinity to Opegrapha, remarks, ^^meo sensu preeter vege- 

 tationem diversam essentialiter differunt excipulo semper aperto, 

 margine jam primitus erecto (tenui) disco planiusculo, habitu 

 Lecideoe v. c. L. corticola. Forma apotheciorum magis polygona 

 quam lirellseformis. Excipulum valde difFert. Opegraphse ge- 

 nuinae Verrucariarum instar incipiunt, nunquam vero Lecanac- 



tides Paucis, si Graphidearum tribus dissolveretur, neg- 



lecta apotheciorum forma, a qua pendet, Opegraphse ad Limbo- 

 rieas, Lecanactides ad Lecideas pertinerent. Hanc quoque cum 

 Lecideis affinitatem generis nomen imponens in mente occulte 

 habuisse videtur Auctor.^' L. Ref. 374. 



1. Lecanactis h/ncea,^schw, Thallus tartareous, pulverulent, 

 white ; lirellae immersed, oblong or lineari-oblong, rounded at 

 each end, simple, curved ; proper margin stout, elevated, wavy ; 

 disk plane, dilated, pruinose; sporidia in asci, eight, fusifonn, 

 7-septate, pale yellow. 



