Flora Unveiled

366 i Flora Unveiled

If genus was the only “natural” taxon created in the beginning, how does one account for
the origin of all the species on earth, let alone the even more numerous varieties? Linnaeus,
a forerunner of Darwin, grappled with this problem his entire career.

The Sexual System of Classification

Linnaeus’s decision to base his new plant classification system on the sexual organs of flow-
ers was not revolutionary but the culmination of an historical trend in taxonomy. Aristotle
had argued that organisms should be grouped according to those traits that best represented
the organism’s teleos. By this he meant the organism’s purpose according to its own self-
interest, not the purpose to which any other organism might put it. It seemed obvious to
Aristotle that the purpose of plants was to reproduce by generating seeds.
Following Aristotle’s principles, the Renaissance botanist Andrea Cesalpino based his
classification system (De Plantis Libri, 1583)  on the “fructification,” by which he meant
fruits and seeds. Flowers he regarded as the “covers” of fruits. In his Historia Plantarum
(1686), John Ray followed Cesalpino’s example, but treated flowers, fruits, and seeds more
or less equally.^44 Joseph Pitton de Tournefort had divided plants into classes based on the
morphology of the corollas, assigning subclasses according to the position of the ovary with
respect to the corolla (inferior vs. superior), but, as in Ray’s scheme, no mention was made of
the sexual role of pollen in his system of classification.
Once news of Camerarius’s experimental confirmation of the sexual theory began to dif-
fuse to European scientific circles, it was inevitable that sexuality would be incorporated
into plant taxonomy. Camerarius had noted the distinct arrangements and numbers of sta-
mens and pistils in different species, but he never applied these traits to a classification sys-
tem. Vaillant was clearly moving in this direction when work on his Botanicon Parisiesnsis
(The Flora of Paris and Environs) was truncated by his untimely death in 1722.^45 In his 1717
lecture, he had cited the number of stamens as an important taxonomic character and given
examples of variations in numerical relationships and positions of the sexual organs in dif-
ferent flowers.
Linnaeus seems to have first learned of Vaillant’s work through his mentor, Johan
Rothman, the district medical officer and physics instructor at the Växjö Gymnasium
where Linnaeus attended school. Rothman recognized Linnaeus’s talents as a botanist
and gave him private tutorials in botany, introducing his eager pupil to the rudiments of
the new sexual theory by providing him with a surprisingly faithful synopsis of Sébastien
Vaillant’s risqué lecture.^46 It is possible that he became further acquainted with it through
excerpts and summaries of Camerarius’s Epistola around this time. Thus, Linnaeus’s early
education played an important role is guiding him toward his sexual system. According to
Erikson,

Even if Linnaeus did not remember exactly what Rothman had taught him, we may

suppose that henceforth there would always be for him a subconscious link between

the two matters— classification and the sexuality of plants.^47

After a frustrating year at the University of Lund, with its meager resources, Linnaeus
transferred to the more prestigious University of Uppsala in 1728, where he soon acquired