Chap. VI] ANIMALS 139 



clumps. Besides this, in opposition to those of the Atta-fungus they 

 regularly develop in a nutritive solution into ordinary hyphae and thus 

 show that they have lost less of their filamentous character. At a still 

 lower stage, in spite of the better definition of their shape as a whole, 

 we find the 'kohlrabi-clumps' of Cyphomyrmex strigatus (Fig. 75). 

 The lowest stage of development, however, is shown in the fungus-gardens 

 of Cyphomyrmex auritus, Apterostigma pilosum, A. Molleri, and A. IV, 

 where the swellings show no strict localization in their arrangement on 

 the hyphae and no constancy in their dimensions. 



A factor so destructive as the parasol-ants in tropical America, in 

 particular near the Equator and north of it, cannot have persisted without 

 influencing the character of the vegetation. The fate of introduced plants 

 is very instructive from this point of view. Many plants are so sought 

 after that their cultivation is quite impossible where parasol-ants are 

 common ; such are rose, orange, coffee, chicory, mango, cabbage ; other 

 plants are comparatively unmolested, 

 such as Eucalyptus, the ramie plant 

 (Boehmeria), grasses, heliotrope, mag- 

 nolia, bay, Cucurbitaceae, wormwood, 



radish, parsley, celery 1 . We must __ . / ■ \ mf 



assume that a similar condition pre- 



vailed in regard to the vegetation of 

 tropical America before the appear- 

 ance of the parasol-ants. The vege- J N ' 

 tation consisted on the one hand of 

 species that were very frequently 

 attacked, and on the other of those J IG ;?f- 'Kohlrabi-clnmps' of the fungus oi 



a South Brazilian hump- backed ant, Cyphomyr- 

 that were seldom or not at all mex strigatus. Magnified 270. After Alf. Moller. 



attacked. The former, unless they 



belonged to the most rapidly growing and commonest species, were 

 either completely annihilated, or persisted only in such examples as 

 owed their individual immunity to some characteristic or other. This 

 characteristic was further selected in the struggle against the parasol-ants. 

 The protective characteristics in many cases may be of a histological 

 nature, as in very fibrous plants, such as grasses, palms, Bromeliaceae, 

 which are included among the plants very rarely or not at all attacked. 

 In other cases, it is probably due to substances that have a sharp taste 

 and smell, or are poisonous, or to very viscous latex rich in caoutchouc, 

 which however is not always protective (Manihot). The number of 

 aromatic plants is relatively very great, as well among those that are 

 sought after as among those that are almost always avoided, a fact 



1 Alf. Moller, op. cit. p. 83. These data refer to South Brazil only. The species of 

 Atta near the Equator may have other preferences. 



