CLASSIFICATION. 277 



parentage ; and the enumeration of those characters is the 

 definition of the species. 



The question next arises, whether, as all Kinds must 

 have a place among the classes, so all the classes in a natural 

 arrangement must be Kinds ? And to this I answer, certainly 

 not. The distinctions of Kinds are not numerous enough to 

 make up the whole of a classification. Very few of the genera 

 of plants, or even of the families, can be pronounced with 

 certainty to be Kinds. The great distinctions of Vascular and 

 Cellular, Dicotyledonous or Exogenous and Monocotyledo- 

 nous or Endogenous plants, are perhaps differences of Kind ; 

 the lines of demarcation which divide those classes seem 

 (though even on this I would not pronounce positively) to go 

 through the whole nature of the plants. But the different 

 species of a genus, or genera of a family, usually have in com- 

 mon only a limited number of characters. A Rose does 

 not seem to differ from a Rubus, or the Umbelliferae from the 

 Ranunculaceae, in much else than the characters botanically 

 assigned to those genera or those families. Unenuinerated 

 differences certainly do exist in some cases ; there are families 

 of plants which have peculiarities of chemical composition, 

 or yield products having peculiar effects on the animal 

 economy. The Cruciferse and Fungi contain an unusual 

 proportion of nitrogen ; the Labiatse are the chief sources of 

 essential oils, the Solanese are very commonly narcotic, &c. 

 In these and similar cases there are possibly distinctions of 

 Kind ; but it is by no means indispensable that there should 

 be. Genera and Families may be eminently natural, though 

 marked out from one another by properties limited in number; 

 provided those properties are important, and the objects con- 

 tained in each genus or family resemble each other more than 

 they resemble anything which is excluded from the genus 

 or family. 



After the recognition and definition, then, of the infinite 

 species, the next step is to arrange those infimce species into 

 larger groups : making these groups correspond to Kinds 

 wherever it is possible, but in most cases without any such 

 guidance. And in doing this it is true that we are naturally 



