370 LICHEN ACEL. [LEcaANoRA. 
Hab. On the trunks of old trees in wooded districts.—Dist, Only in 
S. and W. England; no doubt to be detected elsewhere.—B. M.: Wal- 
thamstow, Essex; Glynde, Sussex; near Bradford, Wiltshire; Windsor 
Great Park, Berkshire. 
b. Thece 8-spored. 
25. L. medians Nyl. Bull. Soc. Bot. Fr. xiii. (1866) p. 367.— 
Thallus orbicular, minutely granulose or leproso-granulose in the 
centre, plicato-radiose at the circumference, opaque, vitelline-yellow 
or citrine, greyish-white in the centre (K—). Apothecia moderate, 
plane, sordid-yellow or yellowish-brown (K—); the thalline margin 
entire or crenulate, citrine ; spores oblongo-ellipsoid, simple, or oc- 
casionally 1-septate, 0,011-17 mm. long, 0,0045-65 mm. thick. 
—Cromb. Grevillea, xviii. p. 45; Leight. Lich. Fl. p. 205, ed. 3, 
p- 189.—Placodium medians Nyl. Bull. Soc. Bot. Fr. ix. (1862) 
p. 262.—Brit. Exs.: Larb. Lich. Hb. n. 59. 
Externally subsimilar to Z. murorum, to which at first sight it seems 
allied, but differs in the absence of any reactions and in the structure of 
the spores. The thallus is at length somewhat expanded, becoming 
almost leproso-dissolved in the centre, which is inspersed with citrine 
granules. It is seldom fertile, though when present the apothecia are 
numerous. 
Hab. On calcareous rocks and walls in lowland and upland districts.— 
Distr. Sparingly in Central and W. England.—B. M.: Pimbury Park, 
Cirencester, Gloucestershire; Llanymynech Hill, Shropshire; Denny 
Abbey, Cambridgeshire. 
26. L. epixantha Nyl. Act. Soc. Linn. Bord. t. xxv. (1864) p. 8. 
—Thallus effuse, thin, granulose, yellow-vitelline or greenish-grey 
(K—), often subevanescent. Apothecia small, sessile, plane or 
slightly convex, yellowish-orange or greenish-yellow (K—); the 
thalline qargin thin, subcrenulate, pale-yellow; spores S8na, 
oblong or ellipsoid, simple, at length polari-locular, 0,012-21 mm. 
long, 0,005-7 mm. thick.—Cromb. Grevillea, xviii. p. 45; Leight. 
Lich. Fl. p. 206, ed. 3, p. 213.—Lecanora vitellina vars. epixantha 
et octospora Nyl., Cromb. Lich. Brit. p. 48; var. epivantha Leight. 
Lich. Fl. p. 181, ed. 3, p. 167. Lecidea epiwantha Ach. Lich. Univ. 
(1810) p. 208. 
Externally scarcely distinguishable from Z. vitelina, but differs defi- 
nitely in the number of the spores. The thallus is entirely absent when 
the plant grows, as it often does, mixed up with other lichens. At times 
the thalline margin of the apothecia is at length excluded. 
Hab. On rocks and walls in maritime and upland situations.— Distr. 
Seen only from a few localities in S. England, Wales, and S. Ireland; no 
doubt overlooked elsewhere, especially when athalline—B. M.: Hastings, 
Sussex; Cheddar, Somersetshire; Llandyssil, Cardiganshire. Giant’s 
Stairs, co. Cork. 
