NOTICES OF BOOKS. 183 



iiiay be in the same relation to as many other Natural Orders. On the 

 other hand, the limits between many of the most natural groups of 

 plants are purely arbitrary, as has been repeatedly shown. Thus the 

 irregukr-flowered Monopetalese, Scrophularinem, Solane(B, AcanthaceiSy 

 and Cyrtandracece, are all artificially divided in books, but in reality are 

 united by numerous osculant genera ; so are the regular-flowered fa- 



Caprifoliace^. 



Saxifi 



many others, are as well entitled to be called Natural Orders as any of 

 the above. 



In Cryptogams the same holds good to a gi'eater degree. The fami- 

 lies Alg^e^ LicJienes^ and Funffi are truly natural, but there are no limits 

 between them. Difficult as the species oi Polypodiacets wcg to define, 

 the genera have hitherto proved impossible ; of Mosses the same holds 

 true. The fact is, there appears to be no appreciable relation between 

 the extent of the natural groups in the vegetable kingdom and the 

 constancy of the characters that separate them. Whether species are 

 originally distinct creations or not is as yet unproven, but there is no 

 difficulty in proving that the greater majority of the generally-admitted 

 genera and Natural Orders are, though natural assemblages, not limited 

 by nature. 



If we now turn to some of the examples given under the articles, it 

 will be seen not only that this uncertainty vitiates the results obtained 

 by M. de CandoUe, but that his information upon the distribution of 

 many Natural Orders is insufficient to draw conclusions from. Under 

 the head of FamiKes whose limits are very restricted sixteen are men- 

 tioned ; of these IRousseacem consists of one genus and one species (con- 



* In the case of logamace<s especially, Mr. Bentham's Paper on this Order, read 

 before the Linn^an Society (March, 185 6), proves that the affinities between all 

 its genera and those of other natural families are so close, that its retention as a 

 natural family is a purely arbitrary exercise of the systematist's prerogative, and that, 

 paradoxical as it may appear, the several genera of Logauiacece are movii allied to 

 plants that are true members of Bubmcece, Gentianece, Apoc^new, etc., than these 

 Natural Orders are io one another. It is because the genera of Loganiacea are 

 more closely allied to each other than those other Orders (in which they find equally 

 close allies) are, as a whole, to one another, that the Natural Order claims an inde- 

 pendent position. In affirming that most Orders are, like genera, arbitrary creations 

 of the systematists, we mean no more than that there is no evidence in the pre- 

 sent state of our knowledge io the contrary; if the Natural Orders are absolutely 

 definable, we are as far from having ascertained the philosophy of their distinc- 

 tions as when Linnaus first alladed to them or Jussicu classified them. Close 

 observation and the study of* development hus done as much to break down some 

 distinctive characters as to establish others. 



