Seed-Scattering 22^^ 



however; but out of ninety-four, upon which the experi- 

 ment was tried, eighteen floated more than twenty-eight 

 days, and some much longer, quite long enough, in fact, 

 to allow of their being carried from one continent to 

 another. 



For Mr. Darwin's estimate of a mile an hour as the 

 rate at which ocean-currents travel was a purposely low 

 one; several of the Atlantic currents travel thirty-three 

 miles a day, and some as much as sixty miles a day, so 

 that any of these eighteen plants might have been carried 

 some hundreds of miles, and others from three to five 

 thousand, without their seeds being any the worse for the 

 voyage. 



Some seeds appear to have no means at all of getting 

 themselves transported from place to place; but it will 

 generally be found that these are seeds which have been 

 altered by cultivation. The grain of wheat and rye, for 

 instance, falls quite naked from the ear as soon as it is 

 ripe, and sinks at once in water; and this is one reason 

 why neither is ever found wild. Rice is a little better off, 

 for each grain is inclosed in a rough, hard case, which 

 effectually preserves it from injury, and probably in its 

 natural state it was able to float on water. But now that 

 its size and weight have been increased by cultivation, it 

 sinks like the others. 



Seeds may occasionally chance to be conveyed across 

 the ocean in drift-wood, without ever coming in contact 

 with the water at all; for stones and small quantities of 

 earth are sometimes found perfectly inclosed; and from 

 the earth thus entangled in the roots of an oak, Mr. Dar- 

 win was able to grow three plants. 



But again, there is another way in which seeds may 



