66 THE HUMAN SIDE OF PLANTS 



abundantly; and a striking thing in its appearance 

 is the reddish-pink colour of its stems. 



Other "petty thieves" are the Castilleja, or 

 painted-cup, Gerardias, and numerous other small 

 plants. 



It is generally known that plants which are whol- 

 ly parasitic in habit have, with a few exceptions, 

 lost their green colouring-matter; and many have 

 lost their leaves. On the other hand, those which 

 are only half parasitic in habit still have the colour- 

 ing-matter in their leaves, but, like the mistletoe, 

 the leaves have a pale greenish tinge, suggestive of 

 degeneration into yellow. 



Plants are likely to become robbers and murder- 

 ers only when driven to it by unavoidable condi- 

 tions, such as are found in the great forests and 

 in the tropical jungles, where the trees and plants 

 are so closely tangled that their heads intermingle, 

 forming an almost impenetrable canopy above and 

 refusing sunlight to the ground plants and less 

 altitudinous trees. These minor plants are forced, 

 in order to live, to fight their way, by fair means 

 or foul, up to the sunlight : unless they do so, they 

 must weaken and die in the gloomy undergrowth 

 below. It is the eternal struggle, the fight to 

 exist, with the lower plants either dying out or de- 

 generating under the oppression of the higher 



