Rev. W. A. Leighton on British Lichens. 9 



Dr. Nylander's specimen are very minute, appressed, and sessile 

 on the upper extremities of the thalline filaments, and of a 

 similar colour, depressed or gyalectoid in the centre, and sur- 

 rounded with a thickish tumid margin, internally pale, and con- 

 sisting of narrow linear-oblong asci interspersed among very 

 slender paraphyses slightly swollen at the apices. Sporidia 8 

 in each ascus, ellipsoid, hyaline. 



Dr. Nylander (/. c.) describes the spermogonia (which I have 

 not seen) as pale, globular or turbinate, and terminal ; spermatia 

 oblong, short ; sterigmata slender. He also says, the hymeneal 

 gelatine becomes blue by the action of iodine, and finally of a 

 vinous red. 



Plate IV. fig. 1, Portion of filament of thallus, magn. 330 times linear, 

 fig. 2. Central axis, magn, 330 times linear, 

 fig. 3. Cells of central axis, magn. 1200 times linear, 

 fig. 4. Asci and paraphyses, magnified 330 times linear, 

 fig. 5. Sporidia, magn. 1200 times linear, 

 fig. 6. Sterigmata and spermatia, after Nylander. 



Spilonema, Born. 

 Thallus filiform, branched, fruticulose; granula gonima large, 

 in transverse strata ; apothecia lecideine, lenticular. 



Spilonema paradoxum, Born. Thallus blackish brown, slender, 

 csespitose, entangled, branched ; apothecia black, terminal, hemi- 

 spherical, immarginate; hypothecium nigrescent; sporidia in 

 asci 8, oblong, simple, colourless ; paraphyses thick, articulate. 



Spilonema paradoxum, Bornet ! Trois Lich. Nouv. p. 4, in Mem. Cherb. 

 Dec. 1856, tab. 1 & 2 ; Nyl. ! Prodr. ] 7 (1857), Syn. 89, t. 2. f. 3 (1858), 

 Scand. 23 (1861); Leight. ! Lich. Brit. Exs. 347 (1868); Mudd, Man. 

 36 (1861). 



On rocks near the Harlech turnpike, at Barmouth, North 

 Wales, June 1856, in fructification. 



Thallus forming larger or smaller, dense or scattered patches 

 of a black olive-brown colour, on the bare surface of granitic 

 rocks, presenting a dense csespitose velvety aspect. Filaments 

 of thallus erect, flexuose, and curved, entangled, irregularly and 

 somewhat secundly branched, about |th of an inch in height. 

 The extremities of the branches, when moistened and viewed 

 under the microscope, are found to consist of a continuous outer 

 membrane, of an olive-tawny colour, within which the large 

 rounded or oblong gonidial cells are seen arranged in tolerably 

 regular transverse strata. The older stems exhibit the gonidia 

 more scattered and irregular, but still disposed in a distinctly 

 transverse direction, and immersed in a dense cellular tissue. 

 Apothecia terminal, minute, hemispherical, without any margin, 

 black ; hypothecium nigrescent. Paraphyses short, thick, arti- 



