76 THE AMERICAN MONTHLY [March 



Take, for instance, the large group of myrmecophilous, 

 that is, ant-loving plants. Here we find bushes and trees 

 harboring armies of ants, which they not only feed with 

 nectar secreted by various organs, but which they house 

 in convenient cavities within their tissues. In the cu- 

 rious trumpet-tree of the West Indies and troj^ical Amer- 

 ica (Cecropia adenopus) each hollow node of the stem 

 forms a chamber in which a number of these honey-lov- 

 ing ants make their nest, a small aperture at the side of 

 the tree giving them free access to this chamber. This 

 aperture, however, is not formed by the plant, it is only 

 indicated to the ants by a slight depression, a special 

 thin portion of the wall, through which the ants eat their 

 way into the hollow stem. Thus the plant is preserved 

 from giving shelter to insects which might misuse the 

 hospitality of the plant. The honey-loving ants alone 

 are taught by some curious "instinct" that a chamber 

 exists for their reception, and thence they make their 

 way. (Fig. 1.) 



At the base of the leaf-stalk will be seen a curious tri- 

 angular fleshy-looking patch, which is found to produce 

 numberless small food-containing bodies, which are, in 

 fact, the inducement held out to the ants to take up 

 their residence in the hollows of the tree. At first sight 

 it would seem as if all the advantages to be gained were 

 on the side of the ants, and we are inclined to ask, what 

 advantage can there be to the tree to entertain and 

 feed these armies of insects ? We look eagerly for some 

 advantage, for we have been taught by all our observa- 

 tions that in plants at least there is no spark of altruism, 

 and that whatever they do they do with a view to bene- 

 fiting themselves. It was the careful observations of 

 Belt and Fritz Miiller on the living trees which led to 

 the solution of this curious problem. It is well known 

 that in tropical countries the leaf-eating ants are per- 



