Species

Species and the Birth of Modern Science 91

Jussieu inuenced many, if not most, of those who followed. He directly inu-
enced botany in general—for instance Samuel Gray’s 1821 A natural arrangement
of British Plants^195 shows how he had become the standard even at the popular level.
He inuenced also the young Cuvier^196 and through him systematics as a whole.
In his early works, he treated species as having more restricted afnity than the
afnity of the genus. He denes species in terms of the sharing of characters, noting,

[j]ust so many plants agreeing in all their parts, or being consistent in their universal

character, and born from and giving birth to those of like nature, are the individuals

together constituting a species, [a term] wrongly used in the past, now more correctly

dened as the perennial succession of like individuals, successively reborn by continued

generation.^197

So here Jussieu is treating the diagnostic aspect of species, which are formed from

individual organisms by abstraction of characters, from the causal aspect of species,

which are, again, a generative reality of like producing like, as he does elsewhere.^198

But it is the Genera plantarum that had the greatest inuence, and in the

Introduction he explicitly denes species, the concept, thus, in a section entitled

“The sure knowledge of species”:

... the species must rst be known, and dened by its proper signs: [it is] a collection

[“adhesio”] of beings that are alike in the highest degree, never to be divided, but sim-

ple by unanimous consent [and] simple by the rst and clearest law of Nature, which

decrees that in one species are to be assembled all vegetative beings or individuals

that are alike in the highest degree in all their parts, and that are always similar

[“conformia”] over a continued series of generations, so that any individual whatever

is the true image of the whole species, past, present, and future. [italics original]^199

He then continues that genera are analogously formed from species that “conform

in a large number of characters.” Species are the only natural rank he recognizes.

Species are simples from which the composite groups are formed. He says, in a sec-

tion entitled “General observation of species afnities”:

As a species unies individuals similar to each other, congeneric species are

expected to follow similar patterns. Yet nobody admits the need to unify [species]

appearance with more numerous marks of conformity, and therefore [those pat-

terns] should [co-]occur with several different norms. This primary reason, before

rst assessment, should demonstrate afnities by classifying [similar] species in

(^195) G ray 1821.
(^196) Stevens 1994, 2, chapter 4.
(^197) Stevens 1994, 292, page 340 in the original, emphasis added. Quotations from Jussieu’s works are
from the translations in this book.
(^198) Jussieu 1964, 311, 313–314.
(^199) Stevens 1994, 356f. The Latin of the definition is:
(^) ... in unam speciem colligenda sunt vegetantia seu individua omnibus suis partibus simillima
& continuatâ generationum serie semper conformia... [Jussieu 1964, xxxvij]