CLASSIFICATION. 313 



tainty to be Kinds. The great distinctions of Vascular 

 and Cellular, Dicotyledonous or Exogenous and Mo- 

 nocotyledonous or Endogenous, are perhaps differences 

 of Kind ; the lines of demarcation which divide those 

 classes seem (though even on this I would not pro- 

 nounce 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 common only a 

 limited number of characters. A Rosa does not seem 

 to differ from a Rubus, or the Umbelliferse from the 

 llanunculacese, in much else than the characters bota- 

 nically assigned to those genera or those families. 

 Unenumerated differences certainly do exist in some 

 cases; there are families of plants which have pecu- 

 liarities of chemical composition, or yield products 

 having peculiar effects on the animal economy. The 

 Cruciferse and Fungi contain an unusual proportion 

 of azote; the Labiatse are the chief sources of essen- 

 tial oils, the Solaneee are very commonly narcotic, &c. 

 In these and similar cases there are possibly distinc- 

 tions of Kind ; but it is by no means indispensable that 

 there should be. Genera and Families may be emi- 

 nently natural, though marked out from one another by 

 properties limited in number; provided those properties 

 be important, and the objects contained in each genus 

 or family resemble each other more than they re- 

 semble anything which is excluded from the genus or 

 family. 



After the recognition and definition, then, of the 

 infimcB species, the next step is to arrange these injimcs 

 species into larger groups : making those groups cor- 

 respond 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 and properly guided, 

 in most cases at least, by resemblance to a type. We 



