IS EUCALYPTUS VARIABLE ? 337 



(1) to create a halo of vapour which checks transpiration, 



(2) to attract, by their odour insects necessary for fertiliz- 

 ing the plant, and (3) render the plant nauseous to some 

 insects and animals which would otherwise prey upon it. 



Such accessory characters cannot obviously be other than 

 variable, yet Messrs. Baker and Smith 1 say "that the con- 

 stituents have been fixed and constant .... "their 

 botanical characters show a marked constancy" . . . 

 "the chemical and botanical peculiarities must also have 

 been fixed primarily." 



The key to the oil question has less to do with the deter- 

 mination of species, but depends on examination of the 

 minute morphology (anatomy) of the leaf. 



V. Botanical Classification for purposes of nomencla- 

 ture of Genera, Species, and Varieties is based on 

 morphological characters. 



It is the object of botanists to construct a Natural 

 System. Linnaeus in proposing his artificial system, which 

 met the requirements of his day, still looked upon a truly 

 natural system as the ideal of botanists. As time has 

 rolled on we have steadily approached this ideal. Jussieu, 

 DeOandolle, Bentham, Hooker, and others have made 

 marked progress in perfecting the natural system, and 

 Engler in his Pflanzenfamilien and now his Pflanzenreich, 

 is, with the assistance of coadjutors, showing the latest 

 progress in this direction. All these authorities base their 

 systems on morphological characters, and it is of course 

 their object to associate closely related forms. 2 



1 This Journal, loc. cit. 



2 I do not lose sight of the fact for one moment that, in the discrimin- 

 ation of genera and species we should call to our assistance any characters 

 that can be employed to that end. Prof. John M. Coulter in his Vice- 

 Presidential Address, Section F. (Biology) Amer. Assoc. Adv. Science, 1891, 

 p. 300, eloquently pleads for a philosophical conception of a species in 



V— Dec. 3, 1902. 



