CHAP, in.] the Dogma of Constancy of Species. 129 



of the flower ; a morphology of the Cryptogams was as little 

 to be thought of in the condition of microscopy before 1820, 

 as the application of the history of development to the 

 establishment of morphological theories. 



De Candolle published his morphology or doctrine of 

 symmetry and his theory of classification together in a book 

 which appeared first in 1813, with the title, 'Theorie Elemen- 

 taire de la botanique ou exposition des principes de la classifi- 

 cation naturelle et de 1'art de decrire et d'etudier les vegetaux,' 

 and again in 1819 in an improved and enlarged edition. 

 The second edition will be the one referred to in the further 

 account of his views. The second chapter of the second book 

 concerns us most at present. After alluding to the fact, that 

 anatomy and physiology are concerned with the structure of 

 the individual organ only so far as the power to fulfil its 

 proper function depends on the structure, he points out that 

 the physiological point of view is no longer sufficient when 

 we are engaged in comparing the organs of different plants. 

 Though it is true that the function of the organs is the most 

 important for the life and permanence of the individual, yet 

 we find these functions modified in the case of homologous 

 organs in different plants ; for the natural classification we 

 must take into consideration only the entire system of organi- 

 sation, that is, the symmetry of the organs. All organisms of 

 a kingdom, he continues, have the same functions with slight 

 modifications ; the immense amount of variation in syste- 

 matically different species depends therefore only on the 

 way in which the general symmetry of structure varies. This 

 symmetry of the parts, the discovery of which is the great 

 object in the investigation of nature, is nothing more than 

 the sum total (Pensemble) of the positional relations of the 

 parts. Whenever these relations (disposition) are regulated 

 according to the same plan, the organisms exhibit a certain 

 general resemblance to one another, independently of the 

 form of the organs in detail ; when this general resemblance 



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