l{cv. W, A. Leighton on the British Umbilicariae. 295 



Gyromium pustulatum, Wiihl. l'\ Upsal. 42-1 (1820); Fl. Suec. 858. 

 Graphis pustulata, Wallr. Crvpt. Germ. '6Ab (1831). 

 Ltisalliu pustulata, Merat, Paris. 202 (183 ); Massal. Mem. 118. 

 Macrodictya pustulata, Massal. Ricerch. 59. fig. 109 (1852). 



On rocks and stones in mountainous districts. By the road 

 from Pemnorvay to Dolbelmen, and under Keven Lees Castle, 

 Dillenius. jNlalvern Hills, Stokes. Old wall, about half way 

 between Caernarvon and Beddgelart, Rev, H. Daiies. Near 

 Biddiston Lighthouse, Cheshire, Mr. Bradbury. Near Halifax, 

 Mr. Bolton. Nant Hevynant Vale, near Snowdon, Turner and 

 Borrer. Near Bautry, L'cland (fruit). Miss Hutchins. L-elaud, 

 Dr. Taylor. Highland mountains of Scotland, Lightfoot. Dart- 

 moor ! Devonshire (fruit), Sir TV. J. Hooker. Hey Tor ! j\Ioel 

 Hebog ! Loch Sligachan, Mr. Borrer. North Wales, Rev. T. 

 Salwey. NessclifFe ! Caer Caradoc ! Shropshire. 



" Thallus a single leaf, attached to the rock by a thick, cal- 

 lous, central disk, orbicular in its youngest state, but afterwards 

 varying from orbicular to ellij^tical, or sometimes quite irregular 

 in its form, from 1 to 8 or 10 inches in diameter ; tlat, except 

 at the edges, where it is elevated, cleft at first into a few, shallow, 

 rounded lobes, which, as the plant grows older, deepen and be- 

 come torn, so as to be entirely shapeless : upper surface pale dull 

 olive-green when moist ; whitish ash-colour, with more or less 

 of a brownish or sometimes of a glaucous tinge, when dry, and, 

 then particularly, palest at the centre ; uneven in every part, 

 except sonietimes for a very small space round the centre, with 

 pustular elevations of the whole substance of the thallus, of 

 an elliptical figure, and varying in size from that of hemp- 

 seed to that of turnip-seed, large and small being mixed 

 together without any order, though they generally decrease in 

 size towards the edges of the thallus ; the whole surface, as well 

 of the pustules as of the interstices, is rough with minute gra- 

 nulations (bearing no slight resemblance, in miniature, to those 

 on the surface of Lycoperdon Proteus), which are most evident 

 at the centre, and scarcely observable in any other part by the 

 naked eye, and produces also scattered clusters of black branch- 

 ing fibres, most numerous towards the border, where they often 

 become confluent ; similar fibres generally lining the edges of 

 any cavities in the thallus, and sometimes that of the whole 

 thallus itself (as re])resented in the upper fig. in E. Bot.), with a 

 beautiful black continuous fringe : under surface brownish olive- 

 green when wet ; when dry, varying from dark brown to ash- 

 colour, and generally slightly pruinose, naked, minutely granu- 

 lated and full of cavities, exactly corresponding with the pustules 

 of the ujjper siu-face, which in some specimens are so numerous, 

 that the under surface has at first sight the ap])earance of a 



