378 



EVOLUTION AND ANIMAL LIFE 



upon trees by means of their flexible stems and branches and 

 are especially noted for possessing appendages in the form of 

 pitchers. These pitcherlike appendages are modified leaves: 

 the normal Dischidia leaf is orbicular, thick, and fleshy. Each 

 pitcher is the blade of a leaf folded so that the lower surface 

 forms the inner surface of the pitcher. Into these pitchers 



FIG. 232. Leaves of Dischidia, which contain adventitious roots of the same plant 

 and in which live colonies of small ants. (From specimens from Philippine 

 Islands.) 



grow adventitious roots that spring from the leaf peduncle. 

 Also in these pitchers live colonies of ants. As rent for furnish- 

 ing these comfortable cozy little ant homes, the Dischidia gets, 

 by means of the adventitious roots in the pitcher, food from 

 the excreta and cadavers of the ants. Hundreds of ants with 

 larvae and pupae can be found in these Dischidia leaves, and 

 without doubt we have here a mutually advantageous sym- 

 biotic adaptation. 



From Weismann's chapter on Symbiosis in his "Vortrage 

 iiber Descendenztheorie," Vol. I, 1902, we translate the follow- 



