222 The Great World's Farm 



planted, are the first trees to spring up upon any newly 

 exposed coral-reef, the nuts having been floated thither 

 from some more or less distant coast. When making 

 experiments to ascertain how long seeds might remain in 

 salt water without being killed, Mr. Darwin was delighted 

 to find that some grew after twenty-one days' immersion. 

 Many ocean-currents, as he reckoned, travel at the rate 

 of a mile an hour, so that these seeds might be floated five 

 hundred miles without being any the worse. But, alas! 

 he had overlooked one thing. The seeds had been under 

 water all this time; and as Dr. Hooker reminded him, '*If 

 they sink, they won't float!" Seeds vary much as to 

 the length of time they are able to remain afloat, and these 

 seeds could not have been transported at all by water, 

 except under different circumstances, such as while they 

 were still inclosed in their seed-vessels, or even attached 

 to the plant or branch on which they grew. 



Some few seeds grew after being kept for one hundred 

 and thirty-seven days in sea water; so that, if able to 

 float, they might have germinated after a voyage of more 

 than three thousand miles — a distance greater than that 

 which lies between Europe and America. 



The question was, then, whether there were any way 

 in which they might float ; and it was found that though 

 ripe, freshly gathered hazelnuts sank directly they were 

 put in water, they would float for as much as ninety days, 

 and then germinate, if they were first dried. 



Now in the natural state, seeds may often be dried by 

 exposure to sun and air before they are washed, or blown, 

 into the water; and they would, some of them at all 

 events, be then perfectly well able to float. 



Drying does not answer the purpose with all plants. 



