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thom in fact an artistic tinge which they wouhl not otherwise have po^ssosseil. 

 However old, then, and from whatever source derived, Cryptogamic vegetation 

 especially, because ascending higher upon the mountains, conserves the 

 surface of rocks and prevents that destruction which would otherwise be 

 their lot. Here on the Malvern Hills, the iVIosses, the Lichens, and the 

 Grasses have almost entirely furred up the rocks, and they cannot now 

 be lowered except by artificial means. In this way rocks become remarkably 

 tinted, and bear in Wales and Scotland the names of Blick or "White, from 

 the hues of the lichens upon them. Monte Rosa, among the Alps, has been so 

 named from its rocks being reddened by cryptogamic jjlants upon them, as I 

 noticed when in Switzerland during the present summer in the vicinity of the 

 chain of Monte Kosa. As high then as vegetation will grow, which is rather 

 more than 9,000 feet in Europe, so far wiU vegetation by an extended growth 

 cover rooks with a protective shield, and above this ice and perpetual snow 

 glazes the rocks with an enduring coat, that is only melted under exceptional 

 circumstances. 



Denudation has in times past prevailed to an astonishing extent, but on 

 the retirement of the sea this has been stopped by the growth of vegetation ; 

 and in modern times only floods under peculiar circumstances, or earthquakes, 

 can make any perceptible difference in the aspect of a country or in any way 

 alter its grand features. Even in a volcanic district vegetation creeps on to the 

 verge of smouldering fires ; and the old craters of Auvergne, in France, are 

 covered with grasses, and, as I have noticed, have now herds of cattle feeding 

 within them, and thus retain their concavities uninjured. So it was with the 

 old crater of Vesuvius previous to the eruption in Pliny's time. Plants, 

 whether flowering or cryptogamic, must then have been migratoi-y from a 

 very early period, and whether any now on the earth are, strictly speaking, 

 endemic, that is, living as natives on the spot where first placed, may, even ia 

 the case of alpine ones, be questioned. Instructed by modern instances, we 

 see in the case of the Canadian water-weed (Anacharis ahinastriun) how a 

 plant may be insidiously introduced into a countiy and so spread as to appear 

 as a true native to present obervation. What is true of the Canadian weed in 

 the present day applies to the common stinging-nettle in former times, which, 

 when once introduced, spread in all directions, and could never be banished 

 or effectually destroyed. In South America at this moment leagues of country 

 are overgrown by European migrating thistles, that would appear to a stranger 

 as truly native as any otlier production he saw. And so in Australia, European 

 weeds have spread to such a degree as to cause an Act of the local Parliament 

 to be passed to attempt {though vainly) their eradication. In like manner 

 the old flora of St. Helena, and other oceanic islands, is dying away, while 

 modern interlopers fill up the ground. This may happen, and no doubt has 

 happened, over and over again. 



We no more see on the earth its primitive vegetation, as originally placed, 

 than we see in the Alps and other mountainous ranges the original conforma- 



