XIV INTRODUCTIOX. 



From this it appears, that out of 173 genera belonging to fourteen 

 Linnean sections, no fewer than forty-three genera, or nearly one 

 quarter, contain species at variance with the characters of the classes 

 and orders in which they are placed. Were general works on Botany 

 examined in the same manner, it would be found that the proportion 

 of exceptions is at least as great as that indicated by the foregoing 

 table, which comprehends only those species, the variations of which 

 are constant and uniform, and does not include mere accidental 

 deviations, such as the tendency of Tetrandrous flowers to become 

 Pentandrous, of Pentandrous to become Tetrandrous, or of both to 

 become Polygamous. 



Although this is not stated for the purpose of extoUing the 

 Natural System at the expense of the Linnean, but rather, as has just 

 been remarked, for the sake of doing away with a vulgar prejudice, 

 yet I cannot forbear expressing my doubt whether any fourteen 

 natural orders can be named in which the proportion of exceptions is 

 so considerable as this, namely, more than one in five. 



Upon the supposed peculiar difficulties of the Natural System I 

 have elsewhere made some general remarks {S7/nupsis, p. x.), which 

 need not be repeated here. It will be better now to inquire more 

 particularly in what the difficulty consists. 



It is said that the primary characters of the classes are not to be 

 ascertained without much laborious research ; and that not one step 

 can be advanced until this preliminary difficulty is overcome. Those 

 who hold a language of this kind must be so unacquainted with the 

 subject, that their arguments, if they can be called by such a name, 

 scarcely deserve a reply. The objection has, however, been made, 

 and must be answered. 



In natural history many facts have been originally discovered 

 by minute and painful research, which, when once ascertained, are 

 readily to be detected by some more simple process, of which Botany 

 is perhaps the most striking proof that can be adduced. The first 

 question to be determined by a student of Botany, who wishes to 

 inform himself of the name, affinities, and uses of a plant, appears 

 to be, whether his subject contains spiral vessels or not, because the 

 two great divisions of the vegetable kingdom, called Vasculares and 

 Cellulares, are characterised by the presence or absence of these 

 minute organs. It is true, we have learned by careful observation, 

 and multiplied microscopical analyses, that vascular plants have 

 spiral vessels, and cellular plants have none ; but it is not true, that 

 in practice so minute and difficult an inquiry needs to be instituted, 

 because it has also been ascertained that all plants that bear flowers 

 have spiral vessels, and are therefore Vascular ; and that vegetables 

 which have no flowers arc destitute of spiral vessels, and arc there- 



