20 PLANT LIFE. 



over the young leaves. If one of these be touched, or a 

 branch shaken, the Httle ants swarm out from the hollow 

 thorns and attack the aggressor with jaws and sting. They 

 sting severely, raising a little white lump that does not 

 disappear in less than twenty-four hours. These ants form 

 a most efficient standing army for the plant, which prevents 

 not only mammalia from browsing on the leaves, but 

 delivers it from the attacks of a much more dangerous 

 enemy — the leaf-cutting ants. For these services the ants 

 are not only housed by the plant, but are provided with a 

 bountiful supply of food ; and to secure their attendance at 

 the right time and place, the food is so arranged and dis- 

 tributed as to effect that object with wonderful perfection. 

 The leaves are bi-pinnate. At the base of each pair of 

 leaflets, on the raid-rib, is a crater-formed gland which, when 

 the leaves are young, secretes a honey-like liquid. Of this 

 the ants are very fond, and they are constantly running 

 about from one gland to another, to sip up the honey as it 

 is secreted. But this is not all; there is a still more 

 wonderful provision of more solid food. At the end of 

 each of the small divisions of the compound leaflet there is, 

 when the leaf first unfolds, a little yellow fruit-like body 

 united by a point at its base to the end of the pinnacle. 

 Examined through a microscope, this little appendage looks 

 like a golden pear. When the leaf first unfolds the little 

 pears are not quite ripe, and the ants are continually going 

 from one to another, examining them. When an ant finds 

 one sufficiently advanced it bites the small point of attach- 

 ment ; then, bending down the fruit-Hke body, it breaks it 

 off and bears it away in triumph to the nest. All the fruit- 

 hke bodies do not ripen at once, but successively, so that 

 the ants are kept about the young leaf for some time after 



