THE MIGRATION OF PLANTS 



183 



for example the parasitic fungi, but they are all present because the 

 dominant plants have made it possible by their control of the en- 

 vironment. 



115. The Migration of Plants.— As we examine various plant 

 communities growing in very different environments we are im- 

 pressed by the fact that nearly all plants seem to be growing in places 

 to which they are very well suited. Where did they all come from 

 and how did they succeed in finding a congenial environment ? The 

 answer to this question is to be found largely in the efficient means 

 that most plants have for disseminating their propagating bodies. 



Fig. 81. — A black spruce tree, an individual of the second type which is 

 composed of millions of cells or individuals of the first type. (Photograph by 

 A. G. Eldredge.) 



Fruits that open at maturity, such as capsules and pods, are called 

 dehiscent fruits while those that do not open at maturity, such as 

 berries and akenes, are called indehiscent. In the case of plants with 

 indehiscent fruits usuallv the entire fruits are disseminated while 

 plants with dehiscent fruits commonly scatter the seeds only. In 

 some plants the seeds are forcibly expelled by the act of dehiscence. 



