144 SAGACITY AND MORALITY OF PLANTS. 



which it receives the name of ' Bull's-horn Thorn ; ' 

 they having a very strong resemblance to the horns 

 of that quadruped. These thorns are hollow, and 

 are tenanted by ants, that make a small hole for 

 their entrance and exit near one end of the thorn, 

 and also burrow through the partition that separates 

 the two horns, so that the one entrance serves for 

 both. Here they rear their young, and in the wet 

 season every one of the thorns is tenanted ; and 

 hundreds of ants are to be seen running about, 

 especially over the young leaves. If one of these 

 be touched, or a branch shaken, the little 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 securely housed by the plant, but are provided 

 with a bountiful supply of food ; and, to secure their 

 attendance at the right time and place, this food is 

 so arranged and distributed as to effect that object 

 with wonderful perfection. The leaves are bi-pinnate. 

 At the base of each pair of leaflets, on the mid-rib, 

 is a crater-formed gland which, when the leaves are 

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



