LICHENS. 123 
the rack of the higher clouds and the howling of 
glacier winds. On the Alps of Switzerland the 
last lichens are to be found on the highest 
summits, attached to projecting rocks, exposed 
to the scorching heats of summer and the fierce 
blasts of winter; and from forty to forty-five 
kinds have been found in spots, surrounded by 
extensive masses of snow, between 10,000 and 
14,780 feet above the level of the sea. It is inter- 
esting to know, that the only plant found by 
Fic. 9.— LECIDEA GEOGRAPHICA. 
Agassiz near the top of Mont Blanc, was the 
Lecidea geographica (Fig. 9), a very beautiful 
lichen, which covers the exposed rocks on the 
sides and summits of all our British hills, with its 
bright-green map-like patches. This species was 
also gathered by Dr. Hooker at an elevation of 
19,000 feet on the Himalayas, and occupied the 
last outpost of vegetation which gladdened the 
