304 



POPULAR HISTORY OF LICHENS. 



ostioles papillate, at length pertuse. Spores broadly oblong, 

 uniseptate, pale. (E. B. 2617.) 



On the trunks of old forest-trees in lowland regions. Its 

 somewhat thick, whitish, continuous thallus appears to con- 

 tain a distinct gonidic layer, a circumstance very unusual 

 among the Verrucarias, whose vegetative system is more 

 generally represented by loosely interwoven filaments and 

 scattered gonidia innate in the bark on which they are deve- 

 loped. Its thecse are long and linear, and its spores ar- 

 ranged in a single, linear series, as in Calicium and SjqJmzto- 

 jj/wron. The spermogones are black, scattered, and promi- 

 nent, the sterigmata delicate ; and the spermatia acrogenous, 

 and of great tenuity. 



Saxicolous species. 

 t JPerithecium entire. 



4. Yerrucaria muralis. Thallus tartareous-farinose, 

 whitish or greyish, effuse, evanescent. Apothecia subglo- 

 bose, minute, immersed, becoming emergent, pruinose, then 

 naked ; ostioles papillate, pertuse. Spores linear-oblong, uni- 

 septate, cellular, greenish- yellow. (E. B. 2G47.) 



On calcareous stones and on the mortar of walls, but 

 not common. 



