112 SYSTEMATIC BOTANY. 
one plant of the genus Trifolium will convey intelligence, to a certain extent, 
concerning every other plant belonging to its 150 species. 
335. 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 arrangement of Classes and Orders. 
336. There are two independent and widely different methods 
of classifying the genera, which have generally been approved, 
namely, the Artificial System of Linneus, and the Natural Sys- 
tem of Jussieu. The former has for its basis those characters 
which are derived from the organs of fructification, leavimg all 
other natural affinities out of view. The latter, on the contrary, 
is founded upon all those natural affinities and resemblances of 
plants, by which Nature herself has distinguished them into 
groups and families. 
~837. In regard to the relative merit of these two arrangements there is now no 
longer room for comparison. That of Linnzeus is truly ingenious and beautiful, 
and furnishes, perhaps, the readiest means for determining 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. 
338. But, in acquiring a thorough and accurate knowledge 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 
formerly embarrassed the science of the vegetable structure, so as to render this 
system unavailable, have now been so far removed by the labors of De Candolle 
and Lindley, in Europe, and of Drs. Torrey and Gray, of our own country, that it 
is brought generally within the scope of the ordinary mind, and shown to be 
founded in true philosophy. Accordingly, it is now generally adopted. 
839. Still, the difficulties attending analysis* by the Natural System alone, — 
are confessedly too great to be successfully encountered at the threshold 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 inac- 
curacies of their definitions. On this account it has been thought best to retain, 
in this work, the artificial characters of the Linnzan Classes and Orders, in the 
* Analysis, as used in botany, denotes the dissection and examination of the organic struc- 
ture of plants, in order to learn their characters, affinities, names, &c. See § 344—348. 
