Rev. W. A. Leiiiiliton on the British Unibilicarisc. 283 



'D 



of the tricfc is often wanting. In old specimens the thallus is 

 sometimes found partially separated into two coats, but much 

 less frequently and remarkably, as in e. erusa. The e(l':;es of the 

 blisters of the cuticle become also now and then detached, and 

 somewhat elevated, so as to give the t/iollns the ajjpearance of 

 being covered with leafy scales." — Lich. Brit. 



Mr. Borrer states that he has sought for the plant in vain in 

 the particular station specified by Mr. Brodie. 



In my own herbarium is a specimen received from Mr. George 

 Dixon, of Great Ayton, Yorkshire, given to him by a friend who 

 collected it somewhere in Scotland ; but I could not ascertain 

 the exact locality by subsequent correspondence. Specimens 

 from Upsal, Sweden, from Fries fil. and i)r. Nylander are iden- 

 tical. 



Plate X. fig. 5 & fig. 5 a. (1. Section of tliaUus and apothecia. 2. Spo- 

 ridia.) 



8. arctica, Ach. Thallus thickish, crenate, slightly lobed, 

 naked on both sides ; upper side greenish-brown, rugged with 

 pustules ; under, blackish-brown, nearly smooth. 



Lichenoides atrum corii Persici instar exasperatum, Dill. 110. t. .30, f. 119, 



fide herb. Dilleniani d. Bon-ero teste (1/41). 

 Gyrophora arctica, Ach. Meth. 10(i. t. 2. f. (5 (180:3) ; L. Univ. 221 ; Sm. 



E. Bot. t. 2-185; Turn. & Borr. Lich. Brit. 225; Sommerf. Suppl. Fl. 



Lapp. 177- 

 Gyromium probnucideum, ^. arcticum, Wahl. Fl. Laj)p. 48.3 (1812), fide spe- 



ciminis a Wahlenbergio seipso recepti teste cl. Smithio in E. Bot. 



t. 2485. 

 Gyrophora proboscideu, /3. arctica, Ach. Syn. 65 (1814); Hook. Br. Fl. 2. 



217. 

 Umbilicaria polymorpha, y. arctica, Sch;cr. Spicil. 88 F. 363 (1823-.36); 



Exs. 556 ! ; Enum. 27 ; Tuckenn. Syn. 71 • 



Rocks in the county of Durham ? ! Mr. Eobson in herb. Burrer. 

 Devonshire? Mr. Hudson. 



" Thallus i)eltatc, Hattish, consisting of a single leaf, affixed to 

 the rocks by a thick, callous, central disk, orbicular, from an inch 

 to two inches or more in diameter; its edges irregularly crenate, 

 divided into a few shallow rounded lobes, and somewhat reflexed : 

 ujtpcr surface of a dull greenish-brown when nicjist, changed by 

 drying to a pale pruinosc grey in the centre, whence it gradually 

 darkens towards the edges, where it is blackish ; or sometimes it 

 is dark brown all over ; naked, everywhere very rugged, with irre- 

 gular pustular elevations of the cuticle, which here and there 

 towards the edges of the thallus has the ai)pearance of having 

 burst, as if from being overstretched, leaving depressed, smooth, 

 undulating interstices ; under surface of a j)aler brown and sidj- 

 pruinosc, black (in our specimens) about the centre, quite smooth 



