On Plants and Insects. 157 



family are fertilised by insects, and possess nec- 

 taries ; but, as Delpino has pointed out, the common 

 Burnet is wind-fertilised, and possesses no honey. 

 So also the Maples are almost all fertilised by in- 

 sects, and produce honey ; but some kinds are 

 wind-fertilised and honeyless. Again, among the 

 Polygonums, some species are insect-fertilised and 

 honey-bearing ; while, on the other hand, the Docks 

 and some others have no honey, and are fertilised 

 by the wind. At first sight it might appear an 

 objection to this view and one reason, perhaps, 

 why the earlier botanists missed the true use of 

 honey may have been the fact that some plants 

 (as, for instance, the Common Laurel) secrete 

 honey on other parts than the flowers. 



4. Belt and Delpino have, I think, suggested the 

 true function of these extra-floral nectaries.* The 

 former of these excellent observers describes a 

 South American 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 mush- 

 rooms 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 nest in 



* I by no means, however, wish to suggest that we as yet fully 

 understand the facts. For instance, the use of the nectary at the 

 base of the leaf of the fern is still quite unexplained. 



