CHAPTER XV 



THE MANY REMARKABLE ARRANGEMENTS BY 

 WHICH PLANTS SECURE CHANGE OF LOCATION 



Dissemination; Fruits 



NE of the most obvious and consequential of the facts 

 about the typical plants is their sedentary habit; 

 they are rooted immovably in one spot. Yet all of the 

 kinds are able at some stage in their lives to change their 

 locations, though the methods whereby this is done are most di- 

 verse, as the following pages will abundantly demonstrate. 



We make sure, first of all, why a change of location is needed. 

 To take the most obvious reason, it is evident that if all of the 

 seeds that any plant ripens were to fall direct to the ground and 

 germinate there, a jungle would result so dense that few, or per- 

 haps none, of the plants could survive. A power to spread from 

 their parents is therefore essential in order that individuals may 

 find space in which to develop. But there are reasons, as well, of 

 a secondary sort. Thus, any kind of plant, whether because it 

 exhausts from the soil some material it needs in its growth, or 

 because it imparts to the earth some excretion injurious to itself, 

 cannot grow a very long time in a single location without deterio- 

 ration of vigor. Again, in an ever-changing world, it is an ad- 

 vantage to any species if it can leave a situation becoming less 

 favorable for its life and migrate to some other that is becoming 

 more favorable. Furthermore, it seems true of plants as of men 

 that an occasional change to different surroundings acts stimu- 

 latingly upon health and adaptability, and therefore is distinctly 



378 



