II. ORDERS AND GENERA. 17 



adoiDting three hundred orders for them. The botanist 

 who treats of the single order Caryophyllacea, may be 

 just as correct in doing so, as is another who treats the 

 same plants under the two orders of Silenacece and Alsi- 

 nacecB. These two sub-orders are quite as separable 

 from each other, as is the united order, or the latter sub- 

 order, from Illecehracece. So again, it is quite as "natu- 

 ral " to group all ferns into the one order of Filices, as it 

 is to separate them into Polypodiacece, Hymenophyllacea, 

 Ophioglossacece, &c. 



And in respect to generic groupings, those of Linneus 

 were in the main equallj' good and natural, as are the 

 more numerous genera into which they have been gradu- 

 ally subdivided by his successors. In example, the Lin- 

 nean genus Scirpus was fully as natural, as is its modem 

 subdivision into Eleocharis and Scirpus ; which by a 

 single obscure character severs in twain the more natural 

 section of single-spiked species, only part of which have 

 the special character of style, by which Eleocharis is 

 arbitrarily separated from Scirpus in books. 



The fact seems to be, that Nature is not a series of 

 groups, but a series of gradations. It is Man who clas- 

 sifies the gradations into groups by severing the series at 

 various steps. Thus, orders and genera ought logically 

 to be regarded only as the conventional arrangements of 

 human knowledge about plants, — as matters of books 

 and herbariums, not things of Divine conception. Yet 

 they are at any rate intended to classify and express the 

 facts of nature, if it is done only by dissevering a series 

 or chain at those points where the links are widest or 

 least coherent, — where Nature is least continuous or 

 gradual. So far as they do effect that intent they cannot 

 be purely optional in their quality, however wide and 

 variable may be the choice as to their quantity. And it 



VOL. IV. ^ 



