164 FORESTRY OF NORWAY. 



lost. From this it may be inferred that unless what 

 has been thus withdrawn, or its equivalent, be restored by 

 the decomposition of rocks allowed to go on while the 

 land lies fallow or is utilised by the culture of some 

 other kind of crop, or by a supply of it in manure, the 

 soil will sooner or later become exhausted of these constitu- 

 ents ; and observation has shown that then the land will 

 no longer yield that crop. So is it with land altogether 

 devoid of constituents required in the production of the 

 same or. other vegetables. And thus is the geographical 

 distribution of trees, and of arborescent as well as of herba- 

 ceous plants, to a great extent determined. 



It may be instructive to bear in mind that what is 

 required for the growth and reproduction of a plant, the 

 seed of which has found its way to any spot, is not only 

 heat and moisture, but these in quantity, defined within 

 a limited range, varying in many cases with the successive 

 stages of germination, growth, flowering, ripening of the 

 fruit, and the casting of the seed, a departure from which 

 at any one of these stages, or at some stages intermediate 

 between them, imperilling the result. But not less essen- 

 tial and necessary to the continued growth of the plant is 

 a soil supplying in appropriate form and in appropriate 

 quantities the nutriment required by the plant. 



' The beautiful indigenous plant, the " lady's slipper," 

 grows/ says Schleiden, ' over all parts of the Swiss Fore 

 Alps, where the soil is formed of the Alpine limestone ; 

 it accompanies the whole Swabian musselkajk, and dis- 

 appears suddenly when we come to the sand of the Jura 

 and keuper formations on this side of the Danube. It 

 next makes its appearance on the musselkalk of Turin- 

 gia, and comes down with that on the Werr as far as the 

 neighbourhood of Gotlengen, and it leaps over the 

 Bunter sandstone of the lower Eichsfeld, and the gran : to o 

 the Upper Hartz, and it again gladdens the eye '/. the 

 wanderer on the calcareous formations eastward >f the 

 Brocken. 



