TREES THAT BUILD CITIES 7 



typical example of this self-willed being, and our 

 own wistaria is subject to the same tendency. 



Besides competition among themselves, the trees 

 have to endure the very formidable depredations of 

 certain underworld elements. There are very 

 vicious criminals in every tree city against which 

 only a weak general police protection is opposed. 

 Grafters, gangsters, thugs, highwaymen, and mur- 

 derers wage incessant war and do incalculable harm. 



Grafters are as common throughout the vegetable 

 world as they are in the human world, and trees 

 are often their victims. Some of them, like the 

 beautiful orchid or our familiar morning-glory, do 

 not take more than the not unkindly support of 

 some tree's strong trunk in their weak-kneed ascent 

 toward light and air. Others, like the mistletoe, 

 go a step further and after abandoning all connec- 

 tion with the ground, send food-seeking roots into 

 the vitals of the oak, the poplar, or the elm. But 

 this is mere petty thievery compared to the incredu- 

 lous rapacity of such plants as the Murderer Liana 

 of the tropics, which actually chokes to death the 

 tree on whose trunk it climbs up to health and 

 strength. 



Parasitic insects reap a heavy toll in a tree city. 

 Several varieties of these pests are always at work 

 among the tree inhabitants. Naturalists believe 



