FRUIT AND SEED DISTRIBUTION 



319 



It is obvious that the more seeds there are scattered, the 

 better are the chances that enough of them will find suitable 

 lodgment to replace the individuals that die each year. On 

 the other hand, to produce excessive seeds would be wasteful, 

 and might under 

 some circumstances 

 neutralize the ad- 

 vantage of num- 

 bers. Thus the 

 orchids, producing 

 relatively many 

 seeds, lose many ; 

 only a very small 

 proportion of them 

 ever develop into 

 new plants. On the 

 whole, the plants 

 that depend upon 

 the wind to scatter 

 their seeds seem 

 to maintain them- 



'9 ® 



o a 



Fig. 147. Seeds scattered by birds 



Birds eat the fruit and discharge the indigestible seeds. 

 /, thistle ; ^, mistletoe ; s, bird cherry ; 4, red-osier dogwood 



selves and to invade 



new regions more successfully than those that depend upon 



other agencies for scattering the new plants. 



Many plants have their seeds distributed by currents of 

 water, — streams of various sizes, or ocean currents, or wind 

 currents acting on the water. Seed plants that grow in swamps 

 or ponds are commonly dependent upon water currents for 

 the dispersal of their seeds. But it seems that many seeds 

 are also spoiled by the water. The coconut, for example, 

 which is often cited as a plant that invades ocean islands by 

 being carried over the sea, is reall}- killed by the salt water. 



