206 Dr Daubeny on the Writings and 



ties between plants, by the number, and not by the importance, 

 of their points of agreement. 



Lastly, the younger Jussieu, in his important memoirs pub- 

 lished in the years 1777 and 1778, laid down correctly the 

 laws which were to determine the relative value of these or- 

 gans, by which he afforded a clew to the principles which had 

 guided himself and his uncle in the classification which they 

 had adopted. 



What remained then for Decandolle to achieve, was the i-e- 

 ducing to certain fixed principles those deviations from the 

 normal structure which are perceived in plants naturally allied 

 — explaining how it happens, that species or genera, which 

 approach each other so nearly in the character of those organs 

 which Jussieu had justly considered the most important, should 

 differ, nevertheless, both with respect to the number, and even 

 sometimes in the entire absence, of parts in the one, which 

 exist in the other. 



In short, whilst Jussieu established the general principles of 

 a correct classification, it remained for Decandolle to remove 

 the difficulties which interfered with their application to par- 

 ticular cases. 



Nor was this all — for Jussieu contented himself, with laying 

 down those practical rules which were to guide future bota- 

 nists in grouping together the several objects which present 

 themselves in the vegetable kingdom, and with affording in 

 his works correct models of classification for others to imitate ; 

 whilst the task which Decandolle undertook, was that of refer- 

 ring to their first principles the rules and practice of this 

 school, explaining thereby the reasons on which they were 

 founded, and vindicating the correctness of the models which 

 they had presented for our imitation. 



" The theory of a natural classification," remarks Decan- 

 dolle, " has never yet been properly set down in print, even 

 by those who have contributed most to advance it. Connected, 

 as it is, with all branches of the science, we can only arrive at 

 it by dint of laborious investigations and continued reflections, 

 of which it ought, at this time of day, to be the groundwork, 

 and not the result. Whatever we are able to learn on the sub- 

 ject may be reduced to certain general ideas, which botanists 



