CETRARIA| PARMELIACE: 151 
Distinguished from the preceding by the reticulate wrinkled upper 
surface. Sometimes the thallus is isidiiferous, especially when 
growing in damp localities. On dry exposed rocks it is of a dark 
chestnut colour. Apothecia have not been found in this country ; 
spermogones are similar to those of C. glawcwm. 
Hab. On rocks in subalpine districts.—Distr. Local among the 
Grampians, Scotland.—B. M. Glen Falloch, Ben Lawers and Craig 
Calliach, Perthshire ; Craig Cluny and Morrone, Braemar, Aberdeen- 
shire ; near Fort William, Invernessshire. 
3. C. diffusa A. L. Sm.—Thallus orbicular, closely appressed, 
finely and densely isidiose in the centre, the lobes naked at the 
circumference, sinuate, narrow, rounded and crenate at the 
apices, greyish- or brownish-white, beneath pale-brown with a 
few long rhizine (K + deep yellow, CaCl—). Apothecia 
marginal, rather small, reddish-brown, the margin crenulate and 
sorediate ; spores ellipsoid, 6-9 pw long, 5-6 pw thick.—Lichen 
diffusus Dicks. Pl. Crypt. fase. iii. p. 17, t. 9, fig. 6 (1793) 
(Web. ?); With. Arr. ed. 3, iv. p. 32. LZ. aleurites Ach. Lich. 
Suec. Prodr. p. 117 (1798); Engl. Bot. t. 858.  Parmelia 
aleurites Ach. Meth. Lich. p. 208 (1803); Hook. FI. Scot. ii. 
p. 54 & in Sm. Engl. Bot. v. p. 203; Mudd Man. p. 98; Leight. 
Lich. Fl. p. 130. P. diffusa S. F. Gray Nat. Arr. i. p. 442 
(1821). P. horrescens Tayl. in Mackay Fl. Hib. ii. p. 144 
(1836); Cromb. in Grevillea vii. p. 98 (1879). Parmeliopsis 
aleurites Cromb. Lich. Brit. p. 37 (1870). Platysma diffusum 
Nyl. in Flora lv. p. 247 (1872); Cromb. in Journ. Bot. x. p, 234 
(1872) & in Monogr. i. p. 222; Leight. Lich. FI. ed. 3, p. 95. 
Exsicc. Dicks. Hort. Sice. fase. xi. n. 23; Leight. n. 47; 
Mudd n. 71. 
Not unlike Parmelia hyperopta (P. alewrites), with which it has 
been often confused. The lobes are frequently almost obliterated by 
the isidia, described by older writers as “farinose.” The apothecia 
are rather rare, but when present are numerous and crowded. The 
spermogones are marginal and prominent, with spores 4 » long and 
1 p» thick. 
There is some uncertainty as to the identity of Weber's Lichen 
diffusus (Spice. Fl. Geett. p. 250), described as “‘farinose and black 
below.’’ Dickson’s specimen and description of L. diffusus, how- 
ever, give priority over L. alewrites Ach. for this species, which name 
has been adopted by Wainio and some others. 
Hab. On old palings, rarely on trunks of trees or among mosses 
on rocks in wooded lowland and upland districts.—Distv. Here and 
there in England, and in the Highlands of Scotland; rare in Ireland. 
—B.M. Wakehurst, Ardingly, Burton Park, Eridge Park and Amber- 
sham, Sussex; Woolmer Forest, Hants; near Windsor, Berks; Stoke 
Park and Sotterly Park, Bucks; Croft Castle and near Hereford, 
Herefordshire ; Gopsall, Leicestershire ; near Oswestry and Ellesmere, 
Shropshire; Cwm Bychan, Merioneth; Baysdale, Cleveland, York- 
shire ; Barcaldine, Argyll; Inverarnan and Crianlarich, Perthshire ; 
Glen Dee, Braemar, Aberdeenshire ; Rothiemurchus, Invernessshire ; 
Dunkerron, Kerry. 
