Species

146 Species

act upon the idea that for practical purposes at any rate species are constant, he can

never hope to give that precision to his characters of organs and functions which is

necessary to render his descriptions useful to others; for in groups where the limits of

species cannot be traced (or, what amounts to the same thing in the opinion of many,

where they do not exist), the object of the systematist is the same as in groups where

they are obvious,—to throw their forms into a natural arrangement, and to indicate

them by tangible characters, whose value is approximately relative to what prevails in

genera where the limitation of species is more apparent.^148

Hooker observed that variation tended to be absent in a particular place or colony

but could often be found globally. He noted, in a passage that Gray marginally wrote

was “opt[issime]!” in his copy:

It is very much to be wished that the local botanist should commence his studies upon

a diametrically opposite principle to that upon which he now proceeds, and that he

should endeavour, by selecting good suites of specimens, to determine how few, not

how many species are comprised in the flora of his district. The permanent differences

will, he may depend upon it, soon force themselves upon his attention, whilst those

which are non-essential will consecutively be eliminated. There is no better way of

proving the validity of characters than by attempting to invalidate them.^149

The professional botanist’s role here was crucial. Hooker, George Bentham,
Ferdinand Mueller, and others were better placed in virtue of having specimens from
across districts and indeed the globe to mark out species than local observers or garden-
ers. Hooker’s later collaborator Bentham early on had a fairly traditional view of species
in natural history—they were created by God, of course, but he took more notice of the
Cuvierian definition of descent from a common ancestor. In his early work as a botanist,
a field he turned to after his logic book^150 failed to garner much contemporary atten-
tion (it got rather more later, when the issue of who invented logical quantification was
being discussed), he was convinced that species could be ranked by a comprehensive
survey of variation.^151 After Darwin, he was not so sure, and eventually he gave up the
idea of a species rank. In 1864, he wrote to Ferdinand von Mueller that “true species are
entirely limited in nature.” As Stevens notes, it made little or no difference to his taxo-
nomic work. However, in an anonymous review of de Candolle’s Geographie Botanique
Raisonée in 1856, he had stated clearly enough that a species was

... a collection of individuals which, by their resemblance to each other, or by other

circumstances, we are induced to believe are descended or may have descended from

one individual or a pair of individuals.^152

What the inducements were, however, were unclear. Bentham almost indicates that

species is a purely operational notion.

(^148) Hooker 1853, viii. Cf. Stevens 1997, loc. cit.
(^149) Hooker and Thomson 1855, 35. Cf. Stevens 1997, 364n362.
(^150) Be nt h a m 1827.
(^151) Stevens 1997, 359.
(^152) Stevens 1997, 360.