364 MEANS OF DISPERSAL. 



spaces of ocean, and which annually migrate — for instance, 

 the millions of quails across the Mediterranean — must 

 occasionally transport a few seeds embedded in dirt adhering 

 to their feet or beaks ? But I shall have to recur to this 

 subject. 



As icebergs are known to be sometimes loaded with earth 

 and stones, and have even carried brushwood, bones, and the 

 nest of a land-bird, it can hardly be doubted that they must 

 occasionally, as suggested by Lyell, have transported seeds 

 from one part to another of the arctic and antarctic regions ; 

 and during the Glacial period from one part of the now 

 temperate regions to another. In the Azores, from the large 

 number of plants common to Europe, in comparison with the 

 species on the other islands of the Atlantic, which stand 

 nearer to the mainland and (as remarked by Mr. H. C. 

 Watson) from their somewhat Northern character, in com- 

 parison with the latitude, I suspected that these islands had 

 been partly stocked by ice-born seeds during the Glacial 

 epoch. At my request Sir C. Lyell wrote to M. Hartung to 

 inquire whether he had observed erratic bowlders on these 

 islands, and he answered that he had found large fragments 

 of granite and other rocks, which do not occur in the 

 archipelago. Hence we may safely infer that icebergs 

 formerly landed their rocky burdens on the shores of these 

 mid-ocean islands, and it is at least possible that they may 

 have brought thither some few seeds of Northern plants. 



Considering that these several means of transport, and 

 that other means, which without doubt remain to be dis- 

 covered, have been in action year after year for tens of 

 thousands of years, it would, I think, be a marvellous fact 

 if many plants had not thus become widely transported. 

 These means of transport are sometimes called accidental ; 

 but this is not strictly correct : the currents of the sea are 

 not accidental, nor is the direction of prevalent gales of 

 wind. It should be observed that scarcely any means of 

 transport would carry seeds for very great distances : for 

 seeds do not retain their vitality when exposed for a great 

 length of time to the action of sea-water; nor could they 

 be long carried in the crops or intestines of birds. These 

 means, however, would suffice for occasional transport across 

 tracts of sea some hundred miles in breadth, or from island 

 to island, or from a continent to a neighboring island, but 

 not from one distant continent to another. The floras of 

 distant continents would not by such means become mjngled j 



