LECANOUA. 



217 



tents becoming homogeneous. Its spermogones occur in the 

 form of minute black tubercles, round which the cortical 

 tissue appears raised or torn ; on section of the white me- 

 dullary tissue they appear as greyish spots. The spermatia 

 are very numerous, straight, and of extreme tenuity, resem- 

 bling masses of needles. 



4. Lecanoea subeusca {sub, somewhat, fuscus, brown). 

 Thallus whitish, somewhat cartilaginous, smoothish or gra- 

 nulate-verrucose ; hypothallus white. Apothecium brownish, 

 frequently becoming blackish, sometimes greyish -pruinose. 

 There are many varieties, or corticolous, saxicolous, and mus- 

 cicolous forms, depending on the varying characters both of 

 the thallus and apothecia. The thallus is sometimes rimulose- 

 areolate, papillose or contiguous, and of a yellowish or green- 

 ish colour ; it may be sorediiferous, or may degenerate into 

 a pulverulent crust, becoming one of the Leprarias of old 

 writers. The apothecia may be crowded or scattered, large 

 or small, of various shades of brown and black, concave, 

 flattened or tumid, naked or pruinose, with a thin or tumid, 

 entire or flexuose, crenulate margin : or they may become 

 abortive and sorediiferous (E. B. 450, var. leucopis). 



One of the commonest Lichens, growing on trees, dead 

 wood, palings, rocks and stones in lowland regions, almost 



