VERRUCARIA. 



303 



bark of a tree) . Thallus leprose, whitish or greyish, very 

 thin, contiguous, effuse. Apothecia small, elliptic-conoid, 

 piano-depressed, spreading at the base ; ostioles papillate, 

 entire or pertuse. Spores of medium size, somewhat resem- 

 ble the figure 8 ; epispore hyaline ; endospores pale yellow. 

 (E. B. 1848, var. analepta.) 



On the bark of the oak, birch, and other forest-trees in 

 lowland regions. The thallus is so thin as to appear absent, 

 the perithecia seeming to rise directly from the bark, upon 

 which the plant grows. The bilocular spores appear formed 

 of two oboval cellules in apposition at their broadest ex- 

 tremities. The epispore seems to be for some time coated 

 with a transparent mucus, which disappears as the spore 

 reaches maturity. The black, point-like spermogones are 

 scattered among the apothecia; their spermatia resemble 

 those of Pertusaria communis. In most Yerrucarias the 

 spermogones are abundant, and resemble in appearance the 

 perithecia, from which they are distinguished by their inferior 

 size. In some Yerrucarias, and various other Lichens, sper- 

 matia and spores have been observed to occur within the 

 same receptacle. 



3. Yerrucaria gemmata {gemmo, to bud). Thallus 

 somewhat thick. Apothecia conical, large, innate at base ; 



