GENERAL IDEAS. 15 



renders the colour of every soil black. Moreover, 

 mould yields in abundance elements of nutrition that 

 are immediately assimilable. 



CLASSIFICATION OF SOILS. As regards the quan- 

 tity of water they contain, soils may be divided as 

 follows : 



Marshy. Those soils which are permanently 

 covered by stagnant water ; they are quite unsuitable 

 for forest vegetation. 



Aquatic. Those that are constantly saturated ; 

 where water appears under the pressure of the foot 

 but is enabled to drain away. In these soils we find 

 the pubescent birch, the mountain pine, the elm, 

 ash, willows, &c. 



Damp. Soils in which water no longer appears 

 under the pressure of the foot, but which never dry 

 up at the surface in any season. They are the home 

 of the peduncled oak, the alder, ash, elm, spruce 

 fir, &c. 



Moist. Those which dry up at the surface but not 

 to a greater depth than six inches ; these soils suit 

 almost every forest tree. 



Dry. These soils dry up to a greater depth ; here 

 we find the common birch, the Scotch pine, the 

 cluster pine, the Austrian, and Aleppo pines, &c. 



According to their compactness, soils are either 

 stiff or light, the former being principally composed 

 of clay or impalpable grains of sand, the latter formed 

 of limestone, or sand more or less gritty; on 

 account of the water they contain, the first are 

 termed cold soils ; the second, for a contrary reason, 

 are designated warm soils. 



