I.] THE USES OF HONEY. 13 



the secretion of honey is the result of developmental 

 energy, which afterwards concentrates itself on the 

 ovary. 



No doubt, however, seems any longer to exist that 

 Sprengel is right in considering that the object is to 

 attract insects, and thus to secure cross-fertilisation. 

 Thus most of the Rosaceae are fertilised by insects, 

 and possess, nectaries, but, as Delpino has pointed out, 

 the genus Poterium, is anemophilous, or wind-fertilised, 

 and possesses no honey. As also the Maples are 

 almost all fertilised by insects and produce honey, 

 but Acer negundo is anemophilous and honey less. So 

 also among the Polygonaceae, some species are 

 insect-fertilised and melliferous, while, on the other 

 hand, certain genera, Rumex and Oxyria. have no 

 honey and are fertilised by the wind. At first 

 sight it might appear an objection to this view that 

 some plants secrete honey on other parts than the 

 flowers. 



Belt and Delpino have, I think, suggested the true 

 function of these extra floral nectaries. The former 

 of these excellent observers describes a South Ameri- 

 can species of acacia : this tree, if unprotected, is apt 

 to be stripped of the leaves by a leaf-cutting ant, which 

 uses them, not directly for food, but, according to Mr. 

 Belt, to grow mushrooms on. The acacia, however, 

 bears hollow thorns, while each leaflet produces honey 

 in a crater-formed gland at the base, and a small, 

 sweet, pear-shaped body at the tip. In consequence, 

 it is inhabited by myriads of a small ant, which nests 

 in the hollow thorns, and thus finds meat, drink, and 

 lodging all provided for it. These ants are continually 



