150 MEANS OP DISPEfiSAL. [Chap. XII. 



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, how- 

 ever, 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 neighbouring island, 

 but not from one distant continent to another. The 

 floras of distant continents would not by such means 

 become mingled; but would remain as distinct as they 

 now are. The currents, from their course, would never 

 bring seeds from ITorth America to Britain, though 

 they might and do bring seeds from the West Indies 

 to our western shores, where, if not killed by their very 

 long immersion in salt water, they could not endure our 

 climate. Almost every year, one or two land-birds are 

 blown across the whole Atlantic Ocean, from North 

 America to the western shores of Ireland and England; 

 but seeds could be transported by these rare wanderers 

 only by one means, namely, by dirt adhering to their 

 feet or beaks, which is in itself a rare accident. Even in 

 this case, how small would be the chance of a seed fall- 

 ing on favourable soil, and coming to maturity! But it 

 would be a great error to argue that because a well- 

 stocked island, like Great Britain, has not, as far as 

 is known (and it would be very difficult to prove this), 

 received within the last few centuries, through occa- 

 sional means of transport, immigrants from Europe or 

 any other continent, that a poorly-stocked island, 

 though standing more remote from the mainland, would 

 not receive colonists by similar means. Out of a hun- 

 dred kinds of seeds or animals transported to an island, 

 even if far less well-stocked than Britain, perhaps not 

 more than one would be so well fitted to its new home, 



