68 Estdblishment of Vegetation at the Surface of the Globe. 



cation of which must ultimately establish immense forests in a 

 soil which might be thought to have been condemned to perpe- 

 tual sterility. 



Such, upon these arid rocks, is the development of vegetation, 

 begun by simple byssi, and some lichens, propagated by tufts 

 of mosses, augmented by herbaceous plants. Their accumulat- 

 ed remains have formed this vegetable mould, now sufficiently 

 tliick that the most vigorous trees may drive their root;5 into it. 

 Following in this manner the progress of vegetation, we have 

 convinced ourselves, that vegetable earth is nothing else than 

 the result of the annual decomposition of vegetables, and that 

 without them it could not have existed ; that nature alone, and 

 not human industry, could have deposited it upon the rock, or 

 the old wall where we have observed it, and where its formation 

 is in a manner executed under our eyes. 



We shall not yet leave those forests^ whose establishment we 

 have followed, from the humble grass or the creeping moss, to 

 the production of the largest vegetables. What an abundance 

 of earth is furnished every year, by the fall of their leaves, and 

 the other remains of vegetation ! It is from this vast magazine, 

 incessantly renewed, that nature derives the substances necessary 

 for fertilizing the plains and valleys. To transport these mate- 

 rials, she makes use of the vehicle of water, of those tempestu- 

 ous rains which precipitate themselves in torrents, or descend in 

 sheets from the summits of the mountains into the deepest val- 

 leys. These waters carry with them the spoils of vegetation, 

 and cover with them the plains which are frequently sterile, cre- 

 taceous, sandy, or stony ; their fertilization, without this means, 

 might have cost Nature ages of labour. 



But the plants which lay the foundations of vegetation upon 

 the rocks, being destitute of roots, could not exist upon arid and 

 mobile sand, to fix the mobility of which, another order of vege- 

 tables is required ; this also has been produced. In place of 

 byssi and lichens, which require a fixed and solid base, we find, 

 as the first plants, several species of gramineae and cyperaceae, 

 whose filiform and cespitose roots are interlaced with one another, 

 bury themselves in the sand, bind it together, mingle their re- 

 mains with it, and render it adapted for the reception of vegeta- 



2 



