112 TAXONOMY. 



CHAP. V. 



THEOKY OF NATURAI. CLASSIFICATION. 



167. 



To the Theory of Natural Classification belong essentially 

 the three following particulars. In the Jirst place, we must 

 be acquainted with the relative importance which belongs to 

 organs, compared with one anotlier ; in the secwid place, we 

 must know the circumstances which might lead the observer 

 to mistake the true nature of organs ; and, in the third place, 

 we must be able to estimate the importance which may be 

 attached to each of the points of view, under which an organ 

 may be considered. 



I. Campariso7i of Organs. 



168. 

 As in organic bodies every part has its relative import- 

 ance, so this importance can have a reference only to the 

 function for which it is destined, and not to things to which 

 it stands in no relation. In classification, therefore, the de- 

 gree of importance of every organ, can be estimated only in 

 relation to those organs which have a reference to the same 

 function. 



169. 



But as the functions of the vegetable kingdom are of two 

 kinds, namely, nourishment, which relates to the maintenance 

 of the individual, and propagation, which relates to the main- 

 tenance of the species, so each of these functions, considered 

 by itself, must have an equal importance ; and a classification, 



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