ON A. LAURENT DE JUSSIEU. ^ I 



— in the Natural 3Iethod this ordei- is reversed, and the charac- 

 ter is made secondary to tlie species. 



The Systematic anthors descend from Classes to Genera, 

 and from Genera to Species, and thus proceed from gene- 

 ral to particular. M. de Jussieu completely overturns this 

 proceeding ; he " rises," according to his own statement, 

 "from particulars to generals." And here lies all the differ- 

 ence between the Artificial and Natural Methods; the former 

 subjugating species to genera, and genera to classes, while on 

 the contrary, the latter make classes depend on genera, and 

 genera on species ; the first renders the facts subservient to 

 ideas, and the second, ideas to the facts. 



In this new path, opened to the science of affinities, 

 M. de Jussieu claims at every step, the attention of the 

 Naturalist. But the secret of his powers lies in the path that 

 he followed. The example of Natural Families, all ready- 

 made, guides our author to the formation of those which are 

 less obvious. In those families which are so natural in the 

 eyes of all botanists, the Grasses, the Composita;, Legutninosce, 

 XJmbellifercB^ &c,, he descries a leading beam of liglit, in their 

 general similarity of structure; every character, which if it 

 Were applied to one of these families should disturb its spe- 

 cies, must therefore be excluded; thus, the first condition on 

 which a character must rest, is that it shall not interfere with 

 the combination of such species as are founded on the tout 

 ensemble of their structure. And this calculation of the rela- 

 tive importance of characters, deduced from their affinities 

 with the general structure, is the principle on which jSI. de 

 Jussieu rests his whole system. The peculiar object of his 

 book is the distribution of genera into families. Tournefort 

 had already collected species into genera ; Linnaeus had 

 given a high degree of regularity and precision to these 

 genera. What was wanting therefore, was to perform for 

 the groups of a higher order, for those very groups which 

 Tournefort and Linnaeus had omitted, what these Naturalists 

 had done for genera. M. de Jussieu distributes all the genera 

 that were known at the time when he wrote, in number nearly 



