528 BOTANY 



upon the petioles special food-bodies which are eaten by the ants. 

 A similar provision is found in a species of Acacia (A. sphceroceph- 

 ala), which provides food-bodies upon its leaves, and develops 

 large hollow thorns which serve as domiciles for the ants (Fig. 493). 



The genus Myrmecodia of Java comprises plants which develop a 

 large tuber-like stem, which contains extensive chambers in which 

 dwell colonies of ants. It was supposed that the formation of these 

 chambers was caused directly by the presence of the ants ; but it has 

 been shown that they may form without the presence of the ants, 

 and that the chambered tuber is probably a provision for storing 

 water, and not primarily an adaptation to shelter the ants. 



The leaf-cutting ants, of which a number occur in the Southern 

 states, offer a very remarkable case of symbiosis, in this instance 

 with a Fungus. The leaves which they cut from various trees are 

 carried into their subterranean dwellings, where they are packed 

 together to form a sort of miniature hotbed, upon which, in course 

 of time, a peculiar Fungus mycelium develops. These Fungi produce 

 at the tips of the hyphae abundant swollen bodies which are greedily 

 eaten by the ants. 



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