222 Plant Life and Evolution 



their hollow stems, or in the case of the Acacia, 

 much enlarged hollow thorns. These trees are sub- 

 jected to the attacks of leaf-cutting ants, which are 

 repelled by the ants living in the trees, whose foliage 

 is thus saved from destruction. Sometimes the trees 

 furnish not only lodging but also board, as there are 

 developed certain peculiar secretions which serve as 

 food for their insect tenants. 



A remarkable form of myrmecophily has been 

 recently studied by Wheeler in a number of ants 

 from Texas and other warmer parts of America. 

 These ants carry into their nests masses of leaf- 

 fragments which they pack together so as to form a 

 sort of miniature hotbed. Upon this mass of fer- 

 menting vegetation there soon appears a peculiar 

 fungus, which grows luxuriantly and produces food 

 bodies upon which the ants feed.* 



REPRODUCTION 



The Necessity for Reproduction. The necessity 

 of some form of propagation for the perpetuation of 

 the species is evident, and many types of reproduc- 

 tion have developed in response to this need. The 

 simplest of all is the ordinary cell fission, the only 



* Professor Wheeler, in his recent book on the structure and 

 habits of ants, has expressed some doubt as to the entire ac- 

 curacy of some of the observations made upon the habits of 

 the tree-dwelling ants. He believes that the adaptations be- 

 tween the ants and the host tree are not so complete as have 

 been assumed. 



