PARMELIA | PARMELIACE 133 
A very common species, easily recognized by the reticulate lines 
on the thallus which are mostly whitish, though sometimes becoming 
darker, and sometimes marked by isidia. Apothecia are very rare. 
Spermogones are minute with spermatia about 7 » long and 1 yp thick. 
There is a sterile form with very narrow crowded laciniwe which are 
sometimes isidioid (f. panniformis Cromb. in Grevillea, xv. p. 75 
(1887)). 
Hab. On trees, walls, rocks and boulders in lowland and upland 
districts. —Distr. General throughout the British Isles.—B. M. Island 
of Guernsey; near Penzance, Cornwall; Dartmoor, Devon; New 
Forest, Hants; Sussex; Malvern Hills, Worcestershire ; Lambeth, 
S. Wales; Dolgelly, Merioneth; Stavely, Westmoreland; Ayrshire ; 
Appin, Argyll; Finlarig, Ben Lawers, Glen Falloch, Abernethy, 
Invertrosachs, Black Wood of Rannoch and Ben Vrackie, Perthshire ; 
Cortachy, Forfarshire; Portlethen, Kincardineshire; Corriemulzie, 
Braemar, Aberdeenshire ; Ben Nevis, Invernessshire; Clare Island 
and Achill Island, Mayo. 
Form furfuracea Scher. Lich. Helv. Spic. p. 455 (1846).— 
Thallus spreading, greyish white, generally densely covered with 
greyish-brown isidia which frequently obliterate the lobes except 
at the circumference, otherwise similar to the species. Var. 
Surfuracea Mudd Man. p. 95 (1861); Leight. Lich. Fl. p. 138 ; 
ed. 3, p. 127. Parmelia horrescens Tay]. in Mackay Fl. Hib. ii. 
p. 144 (1836) pro parte. Lichenoides vulgatissimum cinereo- 
glaucum lacunosum et cirrosum Dill. Hist. Musc. p. 188, t. 24, 
fig. 83, D (1741). 
Hasicc. Bohl. n. 11; Johns. n. 187 ; Larb. Lich. Hb. n, 211 ; 
Leight. n. 46 pro parte. 
More frequent than the species with which it is connected by 
every stage of isidiose development. Frequently fertile, and the 
apothecial margins rough with isidia. 
Hab. On rocks, walls and trees, chiefly in upland districts.— 
Distr. General and common in many parts of the British Isles.— 
B. M. Alderney; near Penzance and Helminton, Cornwall; Throwley 
Down and near South Brent, Devon; Basingstoke and New Forest, 
Hants; Maresfield Common, Eridge Rocks and Ardingly, Sussex ; 
Savernake Forest, Wilts; Charnwood Forest, Leicestershire; Malvern, 
Worcestershire ; Lambeth, S. Wales; Barmouth and near Dolgelly, 
Merioneth; Capel Curig, Carnarvonshire; Anglesea; The Wrekin, 
Shropshire; Chatsworth and near Buxton, Derbyshire; Cleveland, 
Yorkshire; Kentmere, Westmoreland; Keswick, Cumberland; New 
Galloway, Kirkeudbrightshire ; Dalmahoy Crags, near Edinburgh ; 
near Helensburgh, Dumbartonshire ; Appin, Argyll; Trossachs, Ben 
Lawers and near Dunkeld, Perthshire ; Clova and Cortachy, Perthshire ; 
Glen Callater, Morrone, Ben Avon and Craig Coinnoch, Braemar and 
Crathes, Aberdeenshire; Glen Nevis, Invernessshire; Applecross, 
Rossshire; Lambay Island, near Dublin; near Cork; Dunkerron, 
Kerry ; Kylemore, Galway ; Clare Island and Achill Island, Mayo. 
19. P. suleata Tayl. in Mackay Fl. Hib. ii. p. 145 (1836).— 
Thallus orbicular, spreading, laciniate-lobate, the lobes sinuate, 
branched, irregularly imbricate, subtruncate at the apices, 
