WITH AGRICULTURE AND PLANTING. 459 



hand, finds a fitter station on mountains in which sand- 

 stone predominates, where the soil is usually deeper. 

 It would seem to be for a similar reason that the Beech 

 grows in many rocky districts, for example, on the 

 Hartz Mountains, at pretty considerable heights, espe- 

 cially on the sides of valleys which run to the south, 

 while these places do not admit the Oak, which is found 

 in the middle provinces of Sweden and Norway ; while 

 the Beech, on the other hand, grows only in the southern 

 parts. From the deficiency of soil, the Upper Hartz can 

 produce neither the Pinus pinea, nor P. sylvestris; the 

 horizontal roots, however, of the Abies, or Norway Spruce, 

 are content with the small portion of earth which co- 

 vers the greywacke and slate, although they cannot find 

 sufficient hold to protect its lofty trunks from being 

 thrown down by the tempest. In some parts of the Forest 

 of Thuringia, where the covering of loose earth is deep- 

 er than in the Hartz, the Pinus picea, or pitch pine, 

 grows luxuriantly. The common fir, Pinus sylvestris, 

 which attains a great height in proper soil, on the con- 

 trary, is stunted and distorted on rocky mountains, 

 where the roots soon come in contact with the rock. It 

 there loses the character of a tree, and assumes that of a 

 shrub, as in place of a single upright stem, several 

 branches shoot out, and these, not unfrequently, are 

 creeping or bent. 



The different conditions of rocks, especially their struc- 

 ture and their state of cohesion, are of some importance in 

 producing these effects ; for the surface of rocks must be 

 detrimental or impervious to the roots of plants, in pro- 

 portion to the compactness of their structure, and the co- 

 hesion of their parts. Schistose rocks, for example, af- 



