402 Rev. W. A. Leighton on new British Lichens. 
roughened or minutely papillate appearance, arising from the 
chinks which separate the large gonidia-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 ventricose 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 | 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 lavch 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 Baomyces 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 
Lrachylia tigillaris, Fries, in a young scattered state, or has 
