52 FORESTRY OF NORWAY. 



Without homologating these views in any way I avail 

 myself of this as a contribution in aid of my illustration. 

 1 find it equivalent to an allegation that there have been 

 not one but many centres of distribution whence species 

 of plants have been dispersed ; and I find it at once 

 equally convenient, and more in accordance with the views 

 I entertained in regard to the successive development of 

 vegetation upon the earth, to look at this fact through 

 Forbes' theory applied to the genus, and through that of 

 Schouw applied to species. And I may further remark that 

 neither do the views advanced by Forbes and Schouw, nor 

 observed facts, necessitate the supposition that the disper- 

 sion from a recognised centre took place in a regular 

 ever-extending continuous circle. Even the fairy ring to 

 which I have alluded, though maintaining generally the 

 circular form, shows not a continuous regular circular out- 

 line ; often it is broken and it assumes something of a 

 horse-shoe shape, sometimes it bulges out in the form of an 

 oval or an ellipse, and in almost every case the regularity 

 of the figures assumed, whatever it may be, is broken by 

 void species, or by projections, or by both ; and in the 

 wider field of nature we find on the ascent of a lofty 

 mountain that there are linear zones of different forms of 

 vegetation ; while, from the summit, may be seen on the 

 plain, well-defined patches of vegetation conformed to 

 particular geological formations, curved and winding 

 lines of vegetation lining the course of some river or 

 streamlet, or it may be, in a well-defined straight line 

 traversing the plain, and ascending and crossing the moun- 

 tains beyond, covering, but confined to a geological dyke, 

 of different material, filling a crack or rent on the super- 

 ficial stratum of the ground a phenomenon of not unfre- 

 quent occurrence. 



In view of this the geographical distribution of all 

 plants, including trees solitary trees, and trees of dense 

 forests, continuous or far apart, may occasionally be 

 attributed to dispersed seeds having alighted on soil 

 favourably conditioned and favourably situated for the 

 vegetation of the trees there found. 



