214 



BOTANY 



and inflated internodes (Cordia nodosa), or in the labyrinthine passages of their 

 large stem-tubers {Myrmecodia). At the same time the ants are provided with 

 food in the case of the Ceoropias and Acacias in the form of albuminous fatty 

 bodies ("food bodies," Fig. 187, F), and by the Acacias also with nectar. The 

 ants in exchange guard the plants most effectively against the inroads of animal 

 foes as well as against other leaf-cutting species of ants, which, in the American 

 tropics, kill trees by completely and rapidly divesting them of their entire foliage. 

 These same leaf-cutting ants live in symbiosis with a Fungus (Sozites gongylophora). 

 Upon the accumulated leaves ("Fungus-gardens"), according to Moller, the ants 

 make pure cultures of the fungus mycelium, whose peculiar nutritive outgrowths 

 serve them exclusively for nourishment. Other familiar examples of symbiosis 

 are those existing between flowers and birds or insects. The flowers in these 

 instances provide the nourishment, .usually nectar or pollen, but sometimes also 

 the ovules (Yucca-moth and the gall-wasp of the figure), while the animals are 



piG. 187. — Acacia sphaerocephala, I, Leaf and part of stein; S, hollow thorns in which the ant 

 live ; F, food-bodies at the apices of the lower pinnules ; N, nectary on the petiole. (Reduced.) 

 11, Single pinnule with food-body, F. (Somewhat enlarged.) 



instrumental in the pollination. Here also each symbiont is dependent upon the 

 other. In the case of the unintentional dissemination of fruits and seeds by the 

 agency of animals, the symbiotic relations are less close. 



Of all the different processes of supplementary nutrition employed 

 by plants, those exhibited by Insectivorous Plants in the capture and 

 digestion of animals is unquestionably the most curious. Although 

 they are green plants and in positions to provide their own organic 

 nourishment, they have, in addition, secured for themselves, by 

 peculiar contrivances, an extraordinary source of nitrogenous organic 

 matter, by means of which they are enabled to sustain a more vigorous 

 growth, and especially to support a greater reproductive activity, than 

 would otherwise be possible without animal nourishment. It is not 

 accidental that the plants which have become carnivorous are, for the 

 most part, either inhabitants of damp places, of water swamps, and 

 moist tropical woods, or that they are epiphytes. The nitrogenous 



