LICHENS. 221 



for a long time hj this mere leaf-like plant, when they 

 were exploring the northern snows in pursuit of scientific 

 objects. 



An excursion among the Pentland hills furnished us 

 with specimens of the most important members of the 

 succeeding group, that of Cetraria. The Iceland moss is 

 familiar to us all, as contained, dried, in glass jars, in the 

 chemists' shops, and to such of us who have been accus- 

 tomed to attend on invalids, the preparation of strong 

 jelly from this lichen is equally familiar. It is a very 

 important member of the lichen clan, not only for its 

 medicinal but for its nutritive qualities. The Icelanders 

 make a savoury dish of it, beating it with milk, and 

 baking it in cakes. Henderson states that the porridge 

 made from it is the most palatable food to be had in 

 Iceland. Dr. Johnstone in his " Flora of Berwick upon 

 Tweed" asserts that it is used in the manufacture of ship 

 biscuits, preserving them from worms. But familiar as 

 the lichen was to us as an article of commerce, it was a 

 new treasure when growing in upright olive-brown tufts, 

 each frond paler on the under side, and with a fringe of 

 dark hairs (C. islandica, Plate XV., fig. 7). It grew under 

 the shelter of sturdy furze and tufts of heath, and on the 

 high. Scotch mountains. Subalpine moors in Scotland are 

 the only British habitat of this lichen, but it grows more 

 luxuriantly and plentifully in high latitudes. The Snow 

 Cetraria is a very pretty species (C. nivalis, Jig. 8). It is 

 of a very pale buff, almost ivory coloured, and becoming 

 a full sulphur at the base ; it grows upright, and its 

 fronds are narrow and much divided. Our specimens 

 were sent us from the Scotch mountains. The Glaucous 



