402 Rev. W. A. Leighton on new British Lichens. 



roughened or minutely papillate appearance, arising from the 

 chinks which separate the large gouidia-cells from each other. 

 No true ostiolum, as in Verrucaria and Endocarpon, could be 

 detected; but, under a low power of the microscope, the apical 

 surface of the wart-like apothecium presents a' roundish, pale- 

 brown, depressed spot. Under a higher power, this appearance 

 is found to be caused by the cells of the external coating be- 

 coming more scattered and distant from each other, or being 

 irregularly removed or absent altogether, and permitting the 

 inner coat or perithecium to be visible underneath; then, in 

 some instances, a very minute rounded brown dot becomes visi- 

 ble, which in all probability is the ostiolum ; but no pore could 

 be defined. The inner tunic, or perithecium, is of similar but 

 paler citrine colour with the exterior coating, and is formed of 

 smaller and more compacted cells, presenting a somewhat waxy 

 structure. The nucleus is pale and white, filling the perithecium. 

 When gently pressed out of the perithecium, the asci and para- 

 physes are seen to grow in a stellate or radiate manner from a 

 spot at the inner base of the perithecium. Paraphyses very slender, 

 either erect or flexuose and entangled, presenting more or less of 

 a beaded appearance, as if hollow and having minute yellow glo- 

 bules scattered at intervals singly in the interior. Asci of an 

 elongated vcntricose or fusiform shape, tapering towards the 

 apex, distended in the middle, and suddenly contracted at the 

 base into a narrow stalk, filled with innumerable minute sporidia, 

 which I have seen issue from the little base of the ascus (when 

 wounded, I presume,) in feeble intervallated jerks, conglutinated 

 into a narrow riband or thread. Sporidia very minute, narrowly 

 oblong or ellipsoid, either straight or irregularly curved, uni- 

 locular, hyaline, with an indistinct minute nucleus at each ex- 

 tremity, about two and a half times as long as broad. 



This curious and very remarkable Lichen I discovered on a 

 single decorticated larch rail at Middletown, near Craig Breiddin, 

 Shropshire; June 6, 1864. Afterwards (August 4, 1864) I again 

 met with it, on the Stiperstones Hill, Shropshire, growing para- 

 sitically on the thallus of Bceomyces rufus, Ach., in company 

 with Lecidea citrinella, Ach., var. arenicola, Nyl., and (Aug. 10, 

 1864) on larch rails of the railway-fence near the Cemetery, 

 Shrewsbury. In all these localities it occurred in very small 

 quantity, and subsequent repeated researches have hitherto 

 failed to detect more of it. Its extreme minuteness has been, 

 no doubt, the cause of its having been heretofore overlooked ; 

 but now that attention has been drawn to it, it will most pro- 

 bably be found to be not uncommon. 



It most resembles at first sight the granules of the thallus of 

 Trachylia tigillaris, Fries, in a young scattered state, or has 



