black, almost plane, umbonate or usually somewhat plicate or
wrinkled, the margin thin, flexuose ; hypotliecium black ; paraphyses
slender, bluish-green or dark-brown towards the tip s;
spores oblong, colourless or rarely brownish, 3-septate, slight,
constricted a t the septa, sometimes halonate, 0,018-24 mm.
long, 0,008-11 mm. thick ; hymenial gelatine bluish with iodine.
— B k petrmum var. CEderi Mudd Man. p. 220 (1861). Lichen
(Ederi Web. Spicil. PI. Goett. p. 182 (1778) (non Engl. Bot.).
Lecidea (Ederi Ach. Meth. p. 49 (1803); Leight. Lich. El.
p. 329 ; ed. 3, p. 349. L. petrsea subsp. (Ederi Cromb. Lich.
Brit. p. 87.
Exsicc. Leight. n. 187; Larb. Lich. Hb. n. 179.
Often confused with Lecanora Dieksonii (see Part I. p. 476) on
account of the rusty-red colour of the thallus.
Hah. On maritiine and mountainous rocks.—Distr. Not uncommon
throughout Great Britain and Ireland; not recorded from
the Channel Islands.—B. M. Near Launceston, Cornwall; Barmouth
and Dolgelly, Merioneth ; Trefriw, Carnarvonshire ; Lounsdale, Cleveland,
Yorkshire ; King’s Park, near Edinburgh ; Nigg, Kincardineshire;
Ben Vrackie and Ben Lawers, Perthshire; Appin, Argyll;
Glen Callater, Glen Ey and Castleton, Braemar, Aberdeenshire ; Glen
Nevis, Invernessshire; Ballinakiel, Connemara, Galway.
3. Rh. alhoatrum Th. Er. Lich. Arct. p. 237 (1860).—
Thallus effuse, whitish or greyish, somewhat areolate or granular
or almost disappearing (K —, CaCl —) ; hypotballus wanting.
Apothecia small, black, sometimes whitish-pruinose, adnate,
convex, sometimes with a spurious white ma rg in ; hypothecium
dark-brown; paraphyses slender, capitate and dark-brown a t
the tip s ; spores ellipsoid, brown, 1- or 3-septate or irregularly
muriform, not halonate, 0,016-20 mm. long, 0,007-9 mm. th ic k ;
hymenial gelatine deep-blue with iodine.—Lichen alhoater Hoffm.
Enum. Lich. p. 30 (1784). L. corticola Ach. in Yet. Acad.
Handl. 1795, p. 137, t. 5, f. 6 ; Dicks. PI. Crypt, iv. p. 20
(1801); Engl. Bot. t. 1892. Lecidea corticola Ach. Meth. p. 53
(1803); S. P. Gray Nat. Arr. i. p. 469 (1821) pro parte.
Fatellaria leucoplaca DC. PI. Franc, v. p. 347 (1805)? L. alboatra
Fr. Lich. Eur. p. 336 (1831) ; Hook, in Sm. Engl. El. v. p. 180;
Cromb. Lich. Brit. p. 87 (incl. var. leucoplaca); Leight. Lich. PI.
p. 326 (incl. f. leucoplaca); ed. 3, p. 346 (incl. f. populorum).
Diplotomma alboatrum Elot. ex Massal. Bic. Lich. p, 98 (1852);
Mndd Man. p. 218, t. 4, f. 82 (incl. vars. trabellinum and
populorum).
Exsicc. Leight. n. 64 ; Mudd nos. 188 (as Buellia disciformis
var. rugulosa), 191, 192 (var. populorum); Larb. Lich. Hb.
n. 176 ; Johns, n. 396.
A number of forms have been distinguished according to differences
noted in the appearance of the thallus or apothecia. Var. trahinella
(Lecidea alboatra var. trahinella Fr. I. c.) represents a somewhat
warted form of thallus with the apothecia, crowded, often confluent
and immarginate. In var. populorum (Diplotomma populorum
Massal. Eic. Lioh. p. 99 (1852) ; Lecidea parasema var. atliroa Ach.
Meth. p. 36) the thallus is limited and forms whitish patches on the
trunks of poplars and other trees, occasionally also on rooks.
Hah. On trees and palings.—Distr. General and common in
England and the Channel Islands. Apparently rare in Scotland, not
unfrequent in Ireland.—B. M. Shanklin, I. of Wight ; Bovey Tracey,
Devon ; near Lymington, Hants ; Ightham, Kent ; St. Leonard’s
Forest, and Elmer, Middleton, Sussex ; Braxted Park, Langford and
Quendon, Essex ; near Cheltenham and Sapperton, near Cirencester,
Gloucestershire ; Windsor Great Park, Berks ; Nannau, Dolgelly,
Merioneth ; Twycross, Leicestershire ; Montford Bridge near Shrewsbury,
Oswestry ; Wafield, Shropshire ; near Alfrook Churohhill,
Kempsey and Spelohley, Worcestershire ; Tetsworth, Oxfordshire ;
Seething, Norfolk; Bttersgill, Teesdale, Durham; Sowerdale, Cleveland,
Basby and Ayton and near Masham, Yorkshire ; Airds House
Appin, Argyll ; Finlarig, Killin, Perthshire ; Limerick, Clare.
Var. venustum A. L. Sm.—Thallus thickish, white. Apothecia
somewhat larger, immersed, then emerging and subconvex, with
a spurious white margin.—Diplotomma venustum Koerb. Parerg.
Lich. p. 179 (1860). Lecidea calcarea Leight. Lich. El. p. 327 ;
ed. 3, p. 348 (non Lichen calcarius Weis).
Hab. On rooks.—Distr. Eare in the Channel Islands, S. England,
Scotland? and W. Ireland.—B. M. Green Island, Jersey; near
Penzance, Cornwall ; Killree, Clare.
Var. epipolia A. L. Sm.—Thallus white, effuse or limited,
tartareous, cracked-areolate or subpulverulent. Apothecia black,
white- or bluish-grey-pruinose, immersed, then erumpent, a t first
plane, becoming convex, with or without a proper margin, often
with a spurious thalline margin.—Lichen epipolius Ach. Lich.
Suec. Prodr. p. 58 (1798); Engl. Bot. t. 1137. Lecidea epipolia
Ach. Moth. p. 53 (1803) ; S. P. Gray Nat. Arr. i. p. 468.
L. alboatra var. epipolia Schær. Enum. p. 122 (1850); Cromb.
Lich. Brit. p. 87 ; f. epipolia Leight. Lich. El. p. 327 ; ed. 3,
p. 347. Diplotomma alboatrum var. epipolium Mudd Man. p. 218
(1861).
Exsicc. Leight. n. 241 ; Mudd n. 193; Larb, Lich. Hb. nos.
177, 178 (as var. ambigua); Carroll Lich. Plib. n. 2 1 ; Johns,
n. 357.
Often with the appearance of a Lecanora owing to the immersed
apothecia being closely surrounded by the thallus. A number of
forms have been recorded by Leighton and others characterized by
various states of the apothecia and of thalline development ;—f. mar-
garitacea Leight. I. c. (Lecidea margaritacea Ach. Lich. Univ. p. 185
(1810) pro parte ; S. F. Gray Nat. Arr. i. p. 468), the apothecia are more
deeply immersed, with a somewhat more pronounced thalline margin ;
in f. murorum Leight. I. c. p. 848, the apothecia are minute and
also deeply immersed, the thallus thin and pale-yellowish ; f. ambigua
Leight. I. c. (Lecidea ambigua Ach. Lioh. Univ. p. 161) has a thin
cracked sometimes dispersed greyish thallus, the apothecia becoming
superficial and with a proper margin only.