CHAP, in.] the Dogma of Constancy of Species. 127 



time in Geneva, and Pyrame de Candolle was attracted to 

 these studies; among his youthful efforts are some important 

 investigations into the effect of light on vegetation, and the 

 contributions which he made to vegetable physiology in his 

 great work on that subject will be noticed in a later portion of 

 this history. De Candolle turned his attention to all parts of 

 theoretical and applied botany, but his importance for the 

 history of the science lies chiefly in the direction of morphology 

 and systematic botany, and it is this which we will now proceed 

 to describe. 



The amount and compass of De Candolle's labours as a 

 systematic and descriptive botanist exceed those of any writer 

 before or after him. He wrote a series of comprehensive 

 monographs of large families of plants, and published a new 

 edition of De Lamarck's large ' Flore Franchise ' substantially 

 altered and enlarged ; and in addition to these and many 

 similar works and treatises on the geographical distribution 

 of plants, he set on foot the grandest work of descriptive 

 botany that is as yet in existence, the ' Prodromus Systematis 

 Naturalis,' in which all known plants were to be arranged 

 according to his natural system and described at length, 

 a work not yet fully completed, and in which many other 

 descriptive botanists of the last century participated, but none 

 to so large an extent as De Candolle, who alone completed 

 more than a hundred families. It is not possible to give 

 an account in few words of the service rendered to botany by 

 such labours as these ; they form the real empirical basis of 

 general botany, and the better and more carefully this is laid, 

 the greater the security obtained for the foundations of the 

 whole science. 



But a still higher merit perhaps can be claimed for De 

 Candolle, inasmuch as he not only like Jussieu elaborated the 

 system and its fundamental principles in his descriptive works, 

 but developed the theory, the laws of natural classification, 

 with a clearness and depth such as no one before him had 



