ECOLOGY OF FRUITS 195 



240. Study of Transportation by Water Nothing less 



than a long series of observations by the pond-margin and 

 the brookside will suiEce to show how general and impor- 

 tant is the work done by water in carrying the seeds of 

 aquatics. An experiment will, however, throw some light 

 on the subject. 



EXPERIMEXT XX 



Adaptation for Transportation by Water. — Collect fruits of as 

 many aquatic, semi-aquatic, or riverside and brookside species of 

 plants as possible, place them on shallow pans of water, and notice 

 what proportion of all the kinds studied will float. Leave them 

 twenty-four hours or more and see whether all the kinds that floated 

 at first are still afloat. Some desirable fruits for this experiment 

 are aquatic grasses, rushes and sedges, polygonums, water-dock, 

 bur-reed, arrowhead, water-plantain, pickerel-weed, alder, button- 

 bush, water-parsnip (5tum), water-hemlock (^Cicuta), water penny- 

 wort {Hydrocotyle), lotus (^Nelumbo). 



241. Distances traversed by Floating Seeds Ocean 



currents furnish transportation for the longest journeys 

 that are made by floating seeds. It is a well-known fact 

 that cocoa-palms are among the first plants to spring up 

 on newly formed coral islands. The nuts from which 

 these palms grew may readily have floated a thousand 

 miles or more without injury. On examining a cocoanut 

 with a fibrous husk attached, just as it fell from the tree, 

 it is easy to see how well this fruit is adapted for trans- 

 portation by water. There are altogether about a hundred 

 drifting fruits known, one (the Maldive nut) reaching a 

 weight of from twenty to twenty-five pounds. 



242. Burs. — A large class of fruits is characterized by 

 the presence of hooks on the outer surface. These are 



