Hooker and Gre'vUl^s Ferns, 279 



Quinary Arrangements in Natural History, which is at once philosophical 

 and highly interesting. Natural orders are related to each other by so 

 many points, that Linnaeus compared them to countries in a map ; but the 

 affinities of an object, Mr. Colebrooke observes, ramify in every direction, 

 and cannot be well represented on a plain surface. The Dichotomous mode 

 of classification has been so represented. " It proceeds upon a selection 

 of single characters in succession, which, taken affirmatively and negatively, 

 furnish at each step two distinctions ; one for objects possessing the cha- 

 racter in question, the other for such as want it. For example, at the 

 very first step, organic and inorganic substances ; and, thereafter, verte- 

 brate and non- vertebrate animals. So, Cotyledonous and Acotyledonous 

 vegetables ; land, again, Monocotyledonous and Dicotyledonous plants. If 

 the series in which the characters are severally noticed be judiciously 

 chosen, the Dichotomous arrangement, well pursued, supplies a very in- 

 structive key to natural knowledge. Many professedly natural distributions 

 have been so ordered. But a more instructive arrangement is that which 

 exhibits an object in all its bearings; which places it amidst its cognates; 

 and contiguous to them, again, those which approach next in degree of 

 affinity, and thence branching every way to remoter relations." Objects 

 or groups to be so arranged must occupy a space of three dimensions. 

 Were the space so occupied indefinite, and round any given or imaginary 

 point, the form of the group would be considered globular, from the same 

 law of imagination by which the sky seems vaulted, and the universe neither 

 square, nor long, nor angular. Hence, as five points form one of the simplest 

 modes of expressing the centre and superficies (the two poles and the 

 zenith and nadir of a globe), the Quinary arrangement is the simplest distri- 

 bution of a large assemblage of objects. The centre group may be supposed 

 to be the type, and the four circumferential ones so many clusters of related 

 objects. If we imagine no perfect type, and, in consequence, the central 

 group omitted, we shall then have the Quaternary arrangement, which, 

 according to Ocken, a Swedish botanist, is the true natural distribution. 

 Without entering farther into the subject, our readers will, we hope, have 

 distinct ideas of the Dichotomous, Quinary, and Quaternary systems ; and 

 they will see that the Quinary and Quaternary are but different modes of 

 expression for what is essentially a circular, or, more correctly, a'spherical 

 system. These and other systems we shall enter into at greater length, 

 when we conceive our young readers to be sufficiently advanced. In the 

 mean time, it is easy to conceive that the surface of a globe will be repre- 

 sented by three points more easily than by five, and by five less perfectly 

 than by seven or twelve. So that all that seems beyond dispute in the 

 matter is, that the most perfect abstract idea of an arrangement is that in 

 which all the objects composing a group shall be clustered together like a 

 sphere. It should never be forgotten that nature knows only species, and 

 that all systems of arrangement or classification are merely attempts at 

 generalising, for the sake of lessening the trouble of knowing the individuals. 



Hooher, William Jackson, LL.D. Reg. Prof. Bot. Univ. Glasg. and F.R.A. 



and L.S. Lond. ; and Robert Kaye Greville, LL.D. F.R. and A.S. Edinb. 



and L.S. London : Figures and Descriptions of Ferns, principally of such 



as have been altogether unnoticed by Botanists, or as have not yet been 



correctly figured. Fasc. V. Folio. 1/. 5s. plain; 21.2$. coloured. 



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