LECANORA.j LECANO-LECIDEE1. 405 



0,009-12 mm. long, 0,005-7 mm. thick ; paraphyses slender, dis- 

 crete, not clavate at the apices ; hymcnial gelatine bluish, then 

 sordid with iodine. Mudd, Man. p. 149 ; Cromb. Lich. Brit. p. 50 ; 

 Leight. Lich. Fl.p.206,ed. 3, p. 189. ParmeUa galactina Ach. Meth. 

 (1803) p. 190. Lichenoides crustosum, orbiculare, incanum Dill. 

 Muse. p. 135, t. 18. f. 17 B. Brit. Kvs. : Mudd, n. 116 ; Leight. n. 

 400. 



A common plant overlooked by our older authors and rarely appearing 

 in their herbaria s. n. Lichen muralis, along with L. saxicola. At first the 

 thallus is orbicular, small, and squamarioid in appearance ; but it is often 

 little developed, and frequently at length is indeterminate. The apothecia 

 are numerous, crowded towards the centre, and thus often angulose. It 

 is in other respects a rather variable plant, presenting the form and sub- 

 species that follow. 



Hub. On walls and rocks, chiefly calcareous, from maritime to upland 

 districts. Distr. General and common in most parts of Great Britain ; 

 rare in the Channel Islands and in S E. and N.W. Ireland. B. M. : 

 Island of Sark ; Rozel, Jersey. Bury St. Edmund's, Suffolk ; Holloway, 

 London ; Stanmore, Middlesex ; Crystal Palace, Surrey ; Peasemarsh and 

 Hastings, Sussex ; Newlyn Cliff, Penzance aud Withiel, Cornwall ; Cleve 

 Hill and Bathampton Downs, Somersetshire ; Charnwood Forest, Leices- 

 tershire ; Great Malvern, Worcestershire; Shitthal and Oswestry, Shrop- 

 shire ; Island of Anglesea ; near Ayton, Cleveland, Yorkshire. King's 

 Park, Stirling ; Ben Lawers and Craig Tulloch, Perthshire ; Portlethen, 

 Kincardineshire ; Craig Guie, Braemar, Aberdeenshire ; aear Fort 

 William, Inverness-shire. Near Cork; Kylemore Lake, Connemara, co. 

 Galway. 



Form verrucosa Leight. Lich. Fl. ed. 3 (1879), p. 190. Thallus 

 pulvinate, white, the pulvinuli thickish, convex, verrucose, scattered. 

 Apothecia small, immersed, crowded. Cromb. Grevillea, xviii. 

 p. 67. 



Differs in the form of the thicker, dispersed thallus, and in the innate 

 apothecia, resulting probably from the nature of the habitat. It no doubt 

 descends from var. deminuta (Stenh.) Cromb. Journ. Bot. 1885, p. 195, 

 and is subconfluent with Hepp, Exs. n. 901 (left-hand specimen). 



Hab. On calcareous rocks in maritime and upland districts. Distr. 

 Only a few localities in Wales, N.W. England, and the N. Grampians, 

 Scotland. B. M. : Mumbles, near Swansea, Glamorgan ; Great Orme's 

 Head, Carnarvonshire ; Asby, Westmoreland. Craig Guie, Braemar, 

 Aberdeenshire. 



Subsp. 1. L. dissipata Nyl. Bull. Soc. Bot. t. xiii. (1866) p. 368. 

 Thallus macular or indeterminate, very sparingly visible, consisting 

 chiefly of a blackish, subleprose hypothallus. Apothecia small, 

 pale-livid, slightly white-suffused; the thalline margin white, opaque, 

 subentire or obsolctely crenate ; spores ellipsoid, 0,008-12 mm. long, 

 0,004-6 mm. thick ; paraphyses not well discrete. Cromb. Grevillea, 

 xviii. p. 67. 



A peculiar lichen, the only one which with a state of the type occurs 

 in the immediate suburbs of London. In our British specimens, which 



