238 



POPULAR HISTORY OF LICHENS. 



irregular and ramose ; the sperrnatia straight, and very nu- 

 merous. This species is made the type of a new genus by 

 some recent authors, — the genus Buellia of De Notaris, the 

 Diplotomma of Flotow. 



Thalhis distinguished by a persistent, black, delicately 

 fibrillose hypothallus, and by coloured areolce, which 

 are sometimes aggregated into a rimose-areolate crust, 

 bounded by a black margin. 

 4. Lecidea geographica (yrj, the earth, and ypaj>rj, a 

 drawing). Areolae yellow, flat or convex, discrete or con- 

 tiguous. Apothecia arising from hypothallus, crowded be- 

 tween areolae, black without and within, margin of cupular 

 exciple thin. The areolae vary much in size and colour; 

 sometimes they are crowded, contiguous or coalescing, form- 

 ing a more or less chinky crust, or they are scattered inter- 

 ruptedly over the hypothallus ; they may be tumid, verru- 

 caeform, prominently marginate, or pulverulent. The apo- 

 thecia may be flat or tumid, sometimes urceolate. Named 

 from its fancied resemblance to a coloured map. (E. B. 245, 

 var. alpicola.) 



The variety atro-virens, which has small, tumid, discrete 

 areolae, and flat or tumid apothecia, is very common on rocks 

 and stones, especially granitoid (quartzose and micaceous), 



