130 Chapters in Modern Botany CHAP. 



internal furnishing of the ant's nest ; but the subject requires 

 further investigation. 



The destructive leaf-cutters have certain preferences; 

 imported plants, such as oranges, roses, coffee-plants, and 

 mango, are greedily attacked ; Solanaceag and grasses are 

 left untouched, but in South Brazil Schimper found that the 

 guava, a Caladium, Cassia neglecta, and Alchornea iricurana 

 were peculiarly liable to be ruined. It is certain that the 

 presence of ethereal oils and ferments is not always a 

 deterrent to the ants, whatever it may be to snails, else 

 orange, guava, mango, rose, etc., would not be such 

 favourites. There can be little doubt that the leaf-cutters 

 would soon exterminate these and other imported plants if 

 no precautions were used, and it is likely that they have in 

 this way exterminated many indigenous species. The leaves 

 of the common orange and the bitter orange are eagerly 

 used, but those of the mandarine and the lemon are avoided. 

 Thus in the natural course of things the two first would be 

 eliminated, the two last preserved. This may be taken as 

 a good example of the action of natural selection, but we 

 cannot of course ascribe to the influence of the ants the 

 qualities which save the lemon and the mandarine. 



In the province of Canton in China it is the custom to 

 place nests of harmless, tree-inhabiting ants xipon the orange- 

 trees in order to defend these from the attacks of the leaf- 

 cutters. This is but an intentional imitation of what has 

 taken place in the course of nature. For, as Belt has told 

 us, the ants which inhabit various species of Cecropia, Cassia, 

 and other plants serve as a bodyguard against destructive 

 intruders. Let us follow Schimper's account of this 

 " symbiosis." 



Schimper's problem, shortly stated, is whether the plants, 

 which are so constantly furnished with a bodyguard of ants, 

 exhibit structures which can be definitely regarded as adapta- 



