132 



POPULAR HISTORY OF LICHENS. 



1. Roccella tinctoria (tinctura, a colour or dye). Thai* 

 lus round, at length nodulose or warted ; segments simple 

 or bifurcate, naked or sorediiferous ; old thallus frequently 

 becomes much elongated, pendulous or trailing, rarely 

 branched; apothecia lateral. (E. B. 211.) 



Its spermogones are frequently absent ; when •present 

 they are readily recognized as black points scattered over 

 the whitish thallus. They are globular, unilocular, and im- 

 mersed ; their spermatia are linear and feebly curved. There 

 is considerable variety in the form of the apothecia. Some- 

 times they are regularly patellate, resembling the apothecia 

 of Lecidea j at other times they are misshapen tubercles, 

 appearing to have burst through the cortical layer, which 

 forms around them an irregular thalline exciple ; the latter 

 state is the more usual, but is probably an abnormal con- 

 dition of the former. The spores of both are alike, being 

 ellipsoid-oblong, straight or slightly curved, generally qua- 

 drilocular or triseptate, nearly colourless or pale yellow, re- 

 sembling somewhat those of Peltigera and Sticta. Its 

 habitat is maritime rocks ; it grows to a very limited extent 

 on the Isle of Portland, Guernsey, and other points on or 

 near the south coast of England. It is more abundant on 

 the Mediterranean shores, but reaches its maximum deve- 



