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POPULAR HISTORY OF LICHENS. 



2. Opegrapha rupestris (rupes, a rock). Lirellse oblong 

 or ovate, deformed, short, obtuse, variously branched, wider 

 at one extremity ; thecse eight-spored ; spores elavate, 

 rounded at each end, triseptate, pale yellow. (E. B. 2345.) 



On calcareous and arenaceous rocks and stones in various 

 parts of Britain. 



Corticolous species. 



3. Opegrapha varia. Thallus pulverulent, white; lirellse 

 prominent, sessile, round, oblong, elliptic, or elongated and 

 attenuated at each end. Thalamium canaliculate or dilated 

 in the middle, or plane and convex ; proper margins promi- 

 nent, inflexed, sometimes subevanescent ; thecse eight-spored, 

 irregularly obovate or obovate-fusiform, five-septate ; the 

 central cell larger, hyaline, pale yellow. (E. B. 1890, var. 

 notha ; 2280, var. tigrina.) 



A common species on the oak, beech, elm, and other trees 

 in our forests. Its name implies its changeable character : 

 there are several varieties or states, depending on alterations 

 in the character of the lirellse. Its spermogones are some- 

 what similar to those of 0. saxatilis. 



4. Opegrapha atra. Thallus very thin, forming smooth, 

 pale yellow or whitish ocellate patches ; lirellse densely 

 crowded towards the centre of the patch, sessile, depressed, 



