366 DARWINISM 



CHAP. 



per century were carried to an oceanic island, that island 

 might become rapidly overrun by the plant, if the conditions 

 were favourable to its growth and reproduction. It is further 

 objected that search has been made for such seeds, and they 

 have not been found. Professor Kerner of Innsbruck examined 

 the snow on the surface of glaciers, and assiduously collected 

 all the seeds he could find, and these were all of plants which 

 grew in the adjacent mountains or in the same district. In 

 like manner, the plants growing on moraines were found to 

 be those of the adjacent mountains, plateaux, or lowlands. 

 Hence he concluded that the prevalent opinion that seeds 

 may be carried through the air for very great distances " is 

 not supported by fact." ^ The opinion is certainly not 

 supported by Kerner's facts, but neither is it opposed by 

 them. It is obvious that the seeds that would be carried by 

 the wind to moraines or to the surface of glaciers would be, first 

 and in the greatest abundance, those of the immediately 

 surrounding district; then, very much more rarely, those 

 from more remote mountains ; and lastly, in extreme rarity, 

 those from distant countries or altogether distinct mountain 

 ranges. Let us suppose the first to be so abundant that a 

 single seed could be found by industrious search on each 

 square yard of the sui"face of the glacier ; the second so scarce 

 that only one could possibly be found in a hundred yards 

 square ; while to find one of the third class it would be 

 necessary exhaustively to examine a square mile of surface. 

 Should we expect that one ever to be found, and should the fact 

 that it could not be found be taken as a proof that it was not 

 there ? Besides, a glacier is altogether in a bad position to 

 receive such remote wanderers, since it is generally surrounded 

 by lofty mountains, often range behind range, which would 

 intercept the few air-borne seeds that might have been carried 

 fi'om a distant land. The conditions in an oceanic island, on the 

 other hand, are the most favourable, since the land, especially 

 if high, will intercept objects carried by the "svind, and will 

 thus cause more of the solid matter to fall on it than on an 

 equal area of ocean. We know that winds at sea often blow 

 violently for days together, and the rate of motion is indicated 

 by the fact that 72 miles an hour was the average velocity 

 ^ See Nature, vol. vi. p. 164, for a summary of Kerner's paper. 



