THE SURVIVAL OF THE FITTEST 381 



Strangely the birds here have not learned that 

 the fruits on my imported plants are edible, though 

 they have been growing here a number of years. 



The common long or Spanish moss which is 

 placed in the genus Dendropogon hangs from the 

 branches of trees over wide areas in the lower 

 south. In addition to its means of propagation 

 by seeds which are borne on air currents, its long, 

 pendant streamers are constantly being torn off 

 and carried for some distance by winds which 

 lodge them on the limbs of other trees. When- 

 ever they are so landed they throw out roots from 

 any part of the stems which come in contact with 

 the wood and a new plant is born. This is a very 

 common and efficient means of distributing this 

 strange Bromeliad. 



We have several kinds of native plants which 

 are not at all dominant in a wild state but which 

 become decidedly aggressive and assume the 

 character of weeds in cultivated ground. Among 

 these are two or three species of sand burs (Cen- 

 chrus) and a Boerhaavia, all of which are provided 

 with burs and are among our most pestiferous 

 weeds. Almost as soon as the ground is broken, 

 they begin to appear in great numbers and only 



