AGENCIES OF SEED DISPERSAL 355 



The dispersal of seeds by wind, like the dispersal of 

 pollen by wind, involves enormous waste. The chance that 

 the wind will drop seeds on " good ground " is, of course, 

 better than the chance that it will drop pollen on a stigma, 

 yet the wind-blown seeds that perish far exceed in number 

 those that survive. 



Despite its wastefulness, wind is by far the greatest 

 sower of seeds in nature. It is also by far the greatest 

 sower of spores, which are one-celled reproductive bodies. 

 Spores are especially conspicuous in ferns and mosses. 

 The first plants to appear on the new islands which re- 

 sulted from the great volcanic eruption of Krakatao in 1883 

 were wind-sown plants. They were forms of ferns and of 

 other non-seed plants whose abundant, light spores the 

 wind carries far better and farther than it carries even the 

 lightest seeds. 



B. Water. Lakes and oceans and running streams are 

 all agencies by which wide scattering of seeds is accom- 

 plished. Some seeds are especially resistant to the en- 

 trance of water and so are able to remain in water for a 

 long time without sprouting. 



In such a great drainage basin as that of the Mississippi 

 Valley the dispersal of seeds by the streams has much to 

 do with the spread of the same kinds of plants over wide 

 areas. Plants growing near the headwaters of the Ohio, 

 Missouri, or Mississippi may gradually spread, by the water- 

 carriage of their seeds, through the entire system traversed 

 by the water which flows down from their original home. 



Even more far reaching is the dispersal brought about 

 by ocean currents. Seeds are carried along the coasts, 

 from island to island, and even from continent to conti- 



