THE JUSSIEUS AND THE NATURAL METHOD. 265 



imply or exclude one another; tlie presence of a single one, as we have already 

 heard Laurent say, suffices to determine the existence of many, and it is even in 

 this that the most distinctive feature of the method reveals itself. 



Adansou* and others, who censured Laurent for this exclusive preference 

 given to one part among all the rest, were completely at fault. They failed 

 to appreciate that wonderful correspondence through which a character, aptly 

 chosen, far from excluding others, as they apprehended, comprises, implies, involves 

 them, as its consequence, and in proportions always definite, in combinations always 

 fixed. They failed to perceive those subordinations, those obligatory connec- 

 tions, or, as Cuvier at a later period called them, those necessary correlations of 

 parts, which enable us from each to infer the whole, and reciprocally from the 

 whole to infer each — a singular prerogative inherent in the natural method, and 

 which that method, among all others, alone possesses. But by what process 

 had Laurent elevated himself to a knowledge at once so thorough and original, 

 to what might almost seem an instinctive appreciation of characters? Doubtless 

 the catalogue of Trianon had been his first guide, the counsels and conversation of 

 Bernard his earliest and most valued resource. But in the following extract from 

 a short manuscript account of himself, which lies before me, we obtain an insight 

 into the means he had devised for rendering this knowledge peculiarly his own. 



" In 1 773," he says, " a place of botanist being vacant at the Academy of Sci- 

 ences, I was tempted to compose a memoir in order to be admitted to it, and with 

 a view to understand thoroughly what are called families, I determined to take 

 one of them as the subject of my essay. Linnaeus had published his Frag- 

 menta Naturalia or Ordines Natural es ; Bernard de Jussieu had arranged his 

 Families in the garden of Trianon, and Adanson had published his Families 

 des Plantes in 1763. I selected for a subject the family of the Eanunculacesa, 

 adopted by these three authors, and after having studied their catalogues, I 

 reviewed this family in all its characters, and soon recognized that these had not 

 all the same value; that some were constant in all the plants of the family, that 

 others varied only by exception, and that others again Avere more or less variable; 

 whence I concluded that, in comparing them, it was not sufficient to have regard 

 to the number of like characters, but that it was necessary to take into account 

 their unequal value : thus it was that the seed furnished me the first values, the 

 sexual organs, taken together, the second, and the other characters, successively 

 diminishing in proportion, gave me finally more definite ideas on these relations. 

 My memoir, composed by myself alone, but approved by my uncle, was accepted 

 by the Academy and opened its doors to me in March, 1773." 



This work on the characters of the Ranunculacece being finished and published, 

 Laurent immmediately commenced a similar one on the CompositcB, the Graminece, 

 the LeguminoscE, the Uinbdliferce, &:c., families alike natural by the consent of 

 all botanists ; and, this completed, he felt that he was master of the science. 



* "The priuciples of M. Jussieu," says Adanson, "will encounter perhaps some difficulty on 

 the part of botanists who believe that a method, in order to be natural, should found its di- 

 visions on an examination of all tlio parts taken together, without g'iviug to any one an ex- 

 clusive preference over others." (Report of Adanson to the Academy on the first memoir of 

 Laurent de Jussieu.) 



Adanson was, after Bernard de Jussieu, the man of his time who had given most attention 

 to method. In his elaborate work, Families (Its Plantes, he remarks : "In the artificial methods, 

 of which the object was simply to render more facile a knowledge of plants, by disentangling 

 it from the multiplicity of characters, consideration was given to but one or a few of the more 

 general or prominent parts of the fructification, but, in a natural method, the characters, 

 whether of the class, the genus or the species, ought to be taken from all parts, more or less 

 obvious, of the plant." Laurent de Jussieu having one day read a memoir to the Academy, 

 Adansou abruptly remarked that he recognized therein several ideas which lie had liiniself 

 already made public. "I can well believe it," was the calm reply of Laurent; "we studied 

 under the same master." Adanson had, in eflVct, studied under Bernard; m6reover, the 

 plantation of the garden of Trianon dates from 1759, while the Families des I'lantcs appeared 

 in 17Gc!. 



