162 



POPULAR HISTORY OF LICHENS. 



and on the trunks and roots of trees on the shores of Loch 

 Lomond and Loch Fine, in Breadalbane, and similar High- 

 land districts ; in many of these localities it is found in 

 abundant fructification. This species has a superior and 

 inferior cortical layer, the former being dense and leathery, 

 formed of superimposed rows of polyhedral cells very in- 

 timately united; the latter thinner, and formed of more 

 irregular cell-elements. The medullary filaments are almost 

 solid, the central canal very narrow, and the septa remote 

 and thickened. Its spermogones occur on the margin of 

 the thallus in the form of small, smooth, brownish tubercles, 

 with an apical pore or ostiole; spermatia linear, very 

 slightly curved, resembling in tenuity those of Cetraria and 

 Cladonia. Its thecse are elongated and eight-spored ; the 

 spores closely packed, apparently in a spiral manner, fusi- 

 form, blunted at ends, polyseptate, very pale yellow or 

 colourless. Some species of Nephroma occur in the Arctic 

 and Antarctic regions, there attaining a size and beauty 

 which entitle them to rank among the most handsome of 

 Lichens. 



Genus II. PELTIGEBA, Willcl. 

 Gen. Char. Thallus below veined, fibrillose or spongiose, ac- 



