388 MEAN8 OP DISPERSAL. 



nually migrate — for instance, the millions of quails across 

 the Mediterranean — must occasionally transport a few 

 seeds imbedded in dirt adhering to their feet or beaks? 

 But I shall have to recur to this subject. 



As icebergs are knowu 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 trans- 

 ported 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 main- 

 land, and (as remarked by Mr. H. C. Watson) from their 

 somewhat northern character, in comparison with the lati- 

 tude, I suspected that these islands had been partly stocked 

 by ice-born seeds during the Glacial epoch. At my request 

 Sir 0. 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 marvelous 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 nieans 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, cr from a continent to a neighboring 



