PLACODIUM | PHYSIACE® 209 
Ezxsicc. Bohl. n. 118; Carroll Lich. Hib. n. 37; Johns. n. 
322; Leight. n. 212; Mudd n. 99. 
A variable lichen in the form and colour of the thallus and in the 
form of the spores. The apothecia are numerous and chiefly central. 
Spermogones are frequent, especially in the absence of apothecia ;: 
they occupy the tips of papille (Parmelia microthelia Ach. Meth. 
Lich. p. 176 (1803) ).. Hudson’s plant is somewhat doubtful, as it has 
only a greenish leprose thallus. Lightfoot’s description refers to var. 
jlavorufescens as well as to this plant, as he gives habitat ‘‘ some- 
times upon rocks.” 
Hab. On the trunks of trees, chiefly poplars, willows and ash, and 
on old palings in maritime lowland and upland situations.— Distr. 
General throughout the British Isles.—B. M. Guernsey; Cornwall; 
near Plymouth and Ilsham Valley, Torquay, Devon; St. Helen’s and 
Bembridge, I. of Wight; Buckhurst Park, Willingham, Eridge Park, 
Frant and Woolstonbury, Sussex; Halstead, Kent; Stansted Mount- 
fitchet Park, Mark’s Hall and Walthamstow, Essex; Windsor Great 
Park, Berks; Malvern and near Crowle, Worcestershire ; Oswestry 
and Shrewsbury, Shropshire; Garn, Denbighshire; Anglesea; Twy- 
cross and Gopsall Park, Leicestershire ; Ayton and Cleveland, York- 
shire ; Levens, Westmoreland; Newton Riggs, Cumberland; Teesdale, 
Durham ; Hexham and Wansbeck, Northumberland; New Galloway, 
Kirkeudbrightshire ; Largs, Ayrshire ; near Edinburgh; near Inverary 
and Connel Ferry, Argyll; Finlarig, Killin, Perthshire; Abergeldie, 
Braemar, Aberdeenshire ; Clonmel, Tipperary ; Ballynegard, Limerick ; 
near Belfast, Antrim. 
Var. flavovirescens Hepp |. c.—Thallus effuse, thin, plane 
and areolate, or in minute lobulate granules, greenish- or orange- 
yellow (K + crimson). Apothecia generally rather small, plane, 
with a thin thalline entire, rarely crenulate, margin, becoming 
convex, the disc orange-yellow, the margin lighter coloured.— 
L. flavovirescens Wulf. in Schrift. Ges. Naturf. Fr. p. 122 (1788). 
L. erythrellus Ach. Lich. Suec. Prodr. p. 43 (1798) ; Engl. Bot. 
t. 1993. Lecanora erythrella Ach. Lich. Univ. p. 401 (1810); 
Hook. Fl. Scot. ii. p. 49 & in Sm. Engl. Fl. v. p. 186. 
L. aurantiaca var. erythrella Nyl. in Act. Soc. Linn. Bord. 
sér. 3, 1. p. 322 (1856) ; Cromb. Lich. Brit. p. 46; Leight. Lich. 
Fl. p. 217; ed. 3, p. 207; subsp. erythrella Ny]. ex Cromb. in 
Grevillea xviii. p. 45 (1889) & Monogr. i. p. 374. Rinodina 
erythrella S. F. Gray Nat. Arr. i. p. 456 (1821). Lecidea 
erythrella Tayl. in Mackay FI. Hib. ii. p. 130 (1836). Callopisma 
aurantiacum var. flavovirescens Massal. Monogr. Lich. Blast. 
p. 70 (1853) ; Mudd Man. p. 137. 
Exsice. Larb. Lich. Hb. n. 20; Mudd n. 100; Johns. nos. 74, 
102, 103. 
Differing from the species in the habitat and generally in the more 
brightly coloured thallus and smaller apothecia. 
Hab. On rocks and old walls in maritime and inland localities.— 
Distr. Fairly general throughout Great Britain, rare in Ireland. 
—B. M. Near Penzance, Cornwall; Valley of Rocks, Lynton, Devon ; 
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