222 LICHENS. 



cetraria (C. glauca, Plate XV., fig. 9) is common on the 

 holes of trees everywhere. It grows horizontally at first, 

 then lifts the lobes of its broad fronds almost perpendi- 

 cularly, so as to show the dark lining in strong contrast 

 with the glossy glaucous hue of the upper surface. We 

 have found it in Wiltshire, Kent, Herefordshire, York- 

 shire, and in both the lowlands and highlands of Scotland, 

 but never got a specimen bearing fruit. The chestnut 

 apothecias should be found near the margin of the frond, 

 but we have sought them in vain. 



Next in order comes the Orchil group, important as 

 furnishing the species best adapted for dyeing. The 

 Koceella Tinctoria, or Orchil of commerce, was once a 

 source of wealth to the inhabitants of Cornwall and 

 Jersey, where it grows pretty freely, and from it was 

 procured the valuable colouring pigment ; but it is now 

 found that this pigment, as well as that extracted from 

 the Cudbear, can be obtained in greater quantity and 

 better quality from the allied lichens imported from the 

 Canary Islands. The fronds of this lichen are rounded 

 and upright. We found poor dwarfed specimens on the 

 rocks about Looe, but the flat dark apothecia were no- 

 where present. 



But the Fucus-like Roceella we found growing freely 

 on those sea- ward rocks. It is much admired for its pale 

 tint, its fronds are branched and flat, it is a pretty species 

 (R. fuciformis, Plate XV., fig. 10). The Borrera group, 

 so called from the botanist Borrer, who took great pains 

 in studying them, is characterized by the branched and^ 

 torn fronds being channelled beneath, and generally 

 fringed around the margin ; the apotheciae are chestnut 



