YERRUCARIA. 



305 



ft Perithecium dimidiate. 

 § Perithecium incurved at base. 

 % Inner tunic {or exciple) black. 



5. Yerrucaria trachona (rpaxus, rough). An Irish 

 species (from Kerry), having fusiform, three-septate, pale 

 yellow spores. 



^[Tf Inner tunic pale, not black. 



6. Yerrucaria Borreri. A species growing generally, 

 on calcareous stones, having large, broadly oblong, uni- 

 septate, granulate, pale spores. (E. B. 2791.) So named in 

 honour of Mr. Borrer of Henfield, Sussex, one of the most 

 distinguished British Lichenologists. 



§§ Perithecium neither incurved nor spreading at the base. 

 % Inner tunic black. 



7. Yerrucaria umbrina. Thallus thin, uniform, very 

 minutely cracked, at first olive, becoming dark umber-co- 

 loured or blackish, forming ink-like stains on stones (es- 

 pecially granitic) about fresh-water lakes and streams. Apo- 

 thecia numerous, minute, crowded, prominent, conoid, 

 black, somewhat shining. Spores oblong, margined, pale. 

 (E. B. 1499.) 



Its habit resembles that of V. maura, a maritime and 

 very common species. 



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