108 SYSTEMATIC BOTANY. 



one plant of the genus Trifolium will convey intelligence, to a certain extent, 

 concerning every other plant belonging to its 150 species. 



315. Thus the whole vegetable kingdom is grouped into species, and the spe- 

 cies themselves into genera. But natural affinities do not stop here. The genera 

 are still too numerous for the purpose of clear and systematic study. The natu- 

 ralist would therefore generalize still further, and reduce the genera to still fewer 

 and larger tribes or groups. Accordingly he finds, on comparing the genera with 

 each other, that they still possess some characters in common, although, perhaps, 

 of a more general nature than those which distinguish them among each other. 

 These general characters, therefore, serve to associate the genera into a sys- 

 tematic an-angement of Classes and Orders. 



316. There are two independent and widely different methods 

 of classifying the genera, winch have generally been approved, 

 namely, the Artificial System of Linnasus, and the Natural Sys- 

 tem of Jussieu. The former has for its basis those characters 

 which are derived from the organs of fructification, leaving all 

 other natural aflinities out of view. The latter, on the contrary, 

 is founded upon all those natural affinities and resemblances of 

 plants, by wliich Nature herself has distinguished them into 

 groups and families. 



317. In regard to the relative merit of these two arrangements there is now no 

 longer room for comparison. That of Linnasus is truly ingenious and beautiful, 

 and furnishes, perhaps, the readiest means for detennining the names of plants 

 which has ever been devised; but this must be regarded as its principal use. 

 Indeed, its author himself did not design it for any higher end, or claim for it any 

 higher merit. 



318. But, in acquiring a thorough and accurate kno-\dedge of the vegetable 

 kingdom, the Natural System is not only the best, but it is the only method which 

 can be relied upon for this purpose. The obscurity and misconceptions which 

 foimerly embaiTassed the science of the vegetable stracture, so as to render this 

 system una\-ailable, have now been so far removed by the labors of De Candolle 

 and Lindley, in Europe, and of Drs. Ton-ey and Gray, of our own countiy, that it 

 is brought generally within the scope of the ordlnaiy mind, and shown to be 

 founded in true pliilosophy. Accordingly, it is now generally adopted. 



319. Still, the difficulties attending analysis* by the Natural System alone, 

 are confessedly too great to be successfully encountered at the thi'eshold of the 

 science, by him who has it yet to learn. These arise, partly from the obscurity 

 of the characteristic distinctions employed, and partly from the remaining in;ic- 

 curacies of their definitions. On tliis account it has been thought best to retain, 

 in this work, the artificial characters of the Linnsean Classes and Orders, in the 



* Analysis, as used in botany, denotes the dissection and examination of llie organic struc- 

 ture of plants, in order to learn their characters, afFinitics, names, &c. See § 344—348. 



