ACACIA SPH^ttOOEPHALA AND CECBOPIA PELT AT A. 309 



secondly, a little golden pear-shaped body developed at the ex- 

 tremities of some of the leaflets of the bipinnate leaf. In the 

 . enlarged drawing, fig. 2, the general aspect of the pear-shaped 

 bodies is seen. I have ventured to rename these structures (the 

 rations served out to the standing army of ante) food-bodies, in- 

 cluding under this term the analogous structures in Ceeropia 

 immediately to be described. 



A few months ago my father received a letter from llerr Fritz 

 Miiller, the well-known naturalist, residing at St. Catharina, in 

 Brazil ; this letter was published in * Nature/ Feb. 17, 1876, 

 p. 304. Fritz Miiller shows that the ants inhabiting the hollow 

 stems of a Ceeropia mentioned by Mr. Belt are supplied with 

 food-bodies analogous to those of the Acacia. Here the food-bodies 

 are not developed on the tips of the leaflets, but at the base of 

 the petiole of the leaf, on its underside, emerging, as Fritz Miiller 

 says, like asparagus from a bed, out of the cushion of hairs which 

 clothe the pulvinus. The sweet liquid for the ants is not sup- 

 plied by glands, but by the scale-insects kept by the ants in the 

 hollow stem which forms the nest of the colony. Thus we have 

 in Ceeropia the same marvellous protection as in Acacia ; more- 

 over I hope to be able to show that not only are the food-bodies 

 of these widely distinct plants histologically identical, but that 

 they are actually homologous one with the other — though one is 



an appendage to the leaves, the other a growth from the pul- 

 vinus. 



Herr Fritz Miiller had informed my father that he intended to 

 publish an account of the Ceeropia ; and through the courtesy of 

 Dr. Hermann Miiller and his son, I was enabled to see a copy m 

 extenso of Fritz Midler's forthcoming paper. As he does not 

 enter into the minute structure of the food-bodies, it seemed 

 worth while to attempt its investigation ; this I have been for- 

 tunate enough to be able to do through the kindness of Dr. Hooker, 

 who has placed living plants of both the Acacia and the Ceeropia 

 at my disposal. I have worked chiefly at the food-bodies of Acacia, 

 as being easier to manipulate, and also because I learn from Dr. 

 H. Midler that Prof. Strasburger, of Jena, will probably describe 

 those of Ceeropia. 



Acacia spu^bocephala. — The leaf is bipinnate and about 9 

 or 10 centims. in length ; it springs from the base of the gigantic 

 pair of thorns, and bears a minute spine at its upper end. The 

 iood-bodies are developed on the six or seven lower pairs of leaf- 



