OF THE PERUTTAN ANDES. 19 



The fact, which I take to be beyond dispute, that in all the 

 mountain-regions of the earth a comparatively small number of 

 the same vegetable types form prominent, if not predominant, 

 elements in the existing floras, seems to me strong evidence of 

 their great antiquity, even as geologists use that term. Of many 

 of them it may be asserted that they possess no sj^ecial facilities 

 for transport over wide areas of ocean, and it must be remarked 

 that, while in the large majority of cases genera thus widely dif- 

 fused are represented by species differing widely in structure, 

 we yet find that in cases where tbe diffusion appears to have 

 occurred in recent geological times, tbe species themselves have 

 remained unaltered, and scarcely exhibit the amount of change 

 which botanists designate by the term variety. As compared 

 with the historical period, the separation of the British Islands 

 from Northern and Central Europe is an event of high antiquity, 

 though recent in a geological sense. Many species have been 

 exposed to new conditions since that date; -but not a single new 

 species, scarcely even a well-marked variety, bas been developed 

 during the interval. 



I trust that I shall be forgiven if in spite of the great authority 

 attaching to the name of Sir Joseph. Hooker, who in this matter 

 has been followed by Mr. Wallace, I prefer to designate as Cos- 

 mopolitarty rather than Scandinavian^ the types of vegetation of 

 which the only fact certainly known is that they are widely 

 spread throughout the world. In the present state of our know- 

 ledge it is, I think, impossible to form any safe conjecture as to 

 tbeir origin, but there appear to be strong reasons for attributing 

 to tliem a high antiquity. As to some of them, there are grounds 

 for supposing that the colder North Temperate Zone was, if not 

 their original home, the region from which they have migrated in 

 recent times; but of these many may, with more reason, be 

 referred to North America than to Scanditiavia, while as to many 

 others the balance of evidence points to an original home in the 

 high mountains of lower latitudes. 



The constituents of the Andean flora furnished by the genera 

 which I have called Am^ldgean do not demand detailed discussion 

 in this place. Only five or six per cent, of the vegetable popula- 

 tion belong to this class ; they belong chiefly to families that are 

 common to the Old and New Hemispheres, but which do not 

 extend far beyond the tropics. Any explanations that can be 

 offered as to their origin must be, to a large extent, con- 



c2 



