72 SEEDS WAFTED BY WATER. [CH. in. 



flexible, and wrap round the wool of any animal with 

 which they may come in_ contact, so that they form a 

 double means of dispersion. 



In other cases seeds are wafted by water. Of this 

 the Cocoa-nut is one of the most striking examples. 

 The seeds retain their vitality for a considerable time, 

 and the loose texture of the husk protects them and 

 makes them float. Every one knows that the Cocoa- 

 nut is one of the first plants to make its appearance 

 on coral islands, and it is, I believe, the only palm 

 which is common to both hemispheres. 



The seeds of the common Duckweeds (Lemnd) 

 sink to the bottom of the water in autumn, and re- 

 main there throughout the winter ; but in the spring 

 they rise up to the surface again and begin to grow. 



