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vegetable life effectually keeping down and banishing 

 plants of a simpler structure, and of a more sluggish and 

 feeble nature. On the loftiest mountains of the globe 

 they constitute the last remnants of vegetation, the last 

 efforts of expiring nature which fringe around the limits 

 of eternal snow ; and long after the botanist has left 

 behind him the last stunted Alpine flower, blooming like 

 a lone star on a midnight sky, amid the loose crumbling 

 stones of the moraine ; long after the last moss has ceased 

 to deck the brown and lifeless ground with a scarce per- 

 ceptible film of green, his eye, wearied by the universal 

 desolation, rests with peculiar interest and pleasure on 

 the hardy lichens, which clothe every rugged rock that 

 lifts up its head through the avalanche, and which luxu- 

 riate amid " the rack of the higher clouds and the howl- 

 ing of glacier winds." On the Alps of Switzerland the 

 last lichens are to be found on the highest summits, at- 

 tached 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, sur- 

 rounded by extensive masses of snow, between 10,000 

 and 14,780 feet above the level of the sea. It is in- 

 teresting to know, that the only plant found by Agassiz 

 near the top of Mont Blanc, was the Lecidea geographica 

 (Fig. 9), a very beautiful lichen, which covers the ex- 

 posed 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 eyes of the 

 illustrious Humboldt, when standing within a few him- 



