Seed-Scattering 22 1 



These heads are detached from the stalks when ripe, and 

 are whirled over the sands for miles, bounding along on 

 the spines, and dropping their seeds by the way. Often, 

 of course, they are whirled into the w^ater, and there they 

 float, the upper spines catching the wind, and acting as 

 sails. 



Water, indeed, plays a most important part in the dis- 

 persal of seeds, many of which, if carried only a short 

 distance by the wind to begin with, may continue their 

 journey and travel much further if dropped into river or 

 sea, especially if they happen to reach one of the many 

 ocean-currents. 



There are not many seed-bearing plants which grow 

 actually in the water; but one of these, the arrow-head, 

 has seeds which keep afloat a long time, not because they 

 are so remarkably light, but because they are so highly 

 polished as to look and behave as if they had been oiled. 

 They do not even become wet, for water runs off them; 

 and it is not until this polish has been destroyed by much 

 rubbing and long soaking that they can be got to sink. 



The seeds of the water-lilies, white and yellow, are 

 kept afloat for some time by means of air-bubbles. Large 

 fruits often float longer than small ones, and could hardly 

 be transported by any other means than water. 



Then, however, comes the all-important question, how 

 far the seeds are affected by remaining for some time in 

 water; and here again they vary considerably, some being- 

 far more hardy than others. 



The coco-nut, for instance, being inclosed in a mass 

 of fiber, floats weU, and is able to stand immersion in either 

 fresh or salt water for an unusually long time, without 

 losing the power of germinating; and coco-palms, self- 



