154 THE ART OF CULTURE. 



on soils of gneiss, mica-slate, and granite in Bavaria, 

 of clinkstone on the Rhone, of basalt in Vogelsberge, 

 and of clay-slate on the Rhine and Eifel, the finest 

 forests of other trees, which cannot be produced on 

 the sandy or calcareous soils upon which pines 

 thrive. It is explained by the fact that trees, the 

 leaves of which are renewed annually, require for 

 their leaves six or ten times more alkalies than 

 the fir-tree or pine, and hence when they are placed in 

 soils in which alkalies are contained in very small 

 quantity, do not attain maturity.* When we see 

 such trees growing on a sandy or calcareous soil — 

 the red-beech, the service-tree, and the wild-cherry for 

 example, thriving luxuriantly on limestone, we may 

 be assured that alkalies are present in the soil, for 

 they are necessary to their existence. Can we, then, 

 regard it as remarkable that such trees should thrive 

 in America, on those spots on which forests of pines 

 which have grown and collected alkalies for centu- 

 ries, have been burnt, and to which the alkalies are 

 thus at once restored ; or that the Spartium sco^pain- 

 um^ Erysimum latifolium^ Blitumj capitatum^, Senecio 

 viscosus, plants remarkable for the quantity of alka- 

 lies contained in their ashes, should grow with the 

 greatest luxuriance on the localities of conflagra- 

 tions ?f 



Wheat will not grow on a soil which has produced 

 wormwood, and, vice versa, wormwood does not 

 thrive where wheat has grown, because they are 

 mutually prejudicial by appropriating the alkalies 

 of the soil. 



One hundred parts of the stalks of wheat yield 



* One thousand parts of the dry leaves of oaks yielded 55 parts of 

 ashes, of which 24 parts consisted of alkalies soluble in water ; the 

 same quantity of pine -leaves gave only 29 parts of ashes, which con- 

 tain 46 parts of soluble salts. (De Saussure.) 



t After the great fire in London, large quantities of the Erysimum 

 latifolium were observed growing on the spots where a fire had taken 

 place. On a similar occasion the Blitum capitatum was seen at Copen- 

 hagen, the Senecio viscosus in Nassau, and the Spartium scoparium in 

 Languedoc. After the burnings of forests of pines in North America, 

 poplars grew on the same soil. — L. 



