The Linnaean Era j 373373 373
and contains its essence, a genus is defined as a group of species that share the same medulla,
derived from the same maternal ovule. In contrast, species are defined as groups of plants
with different cortical material, having been fertilized by different fathers. Because genera
are defined by the mother, the offspring of any intergeneric cross should always be assigned
to the genus of the mother. And since Linnaeus regarded genus as the only natural taxon,
his theory implied that matrilineal descent was part of God’s plan for plants. One could even
argue that Linnaeus’s concept of the matrilineal descent of plant genera trumped his patri-
lineal assignment of class because he considered class to be an artificial taxon. Steeped as he
was in the classical tradition, Linnaeus intuitively must have believed that it was self- evident
that fruit- bearing plants are female at their “core.”^68Linnaeus’s New Theory for the Origin of Species
In Fundamenta Fructificationis (1762), Linnaeus unveiled a new theory for the origin of
species, which in many ways was a forerunner of modern evolutionary theory. The fixity of
species doctrine was jettisoned. At the time of the Creation, according to Linnaeus, there
was only one plant species for each natural order. In other words, there were only as many
species as there were orders. This reduced the number of plant species in the Garden of
Eden to a more manageable number. Note that the original species in Paradise, accord-
ing to Linnaeus’s new theory, represented the “natural orders,” which, in his sexual sys-
tem, were defined by the number of pistils. These orders/ species began to hybridize with
one another until they produced all the genera, and initially there was only one species per
genus.^69 Intergeneric crosses followed, giving rise to more and more species. Each species
was assigned to the genus of the mother. Finally, crosses between different species belonging
to the same genus resulted in the formation of varieties. Linnaeus now regarded varieties as
stable and permanent rather than the unstable effects of local environmental conditions.
Linnaeus’s elaborate hybridization theory of the origin of species never gained trac-
tion. Nevertheless, the general principle it embodied— that modern species evolved from
ancestral species over many generations by a mechanism involving sexual reproduction—
represented a clear break with the fixity of species doctrine, making it an early forerunner of
Darwinian theory. Ironically, Linnaeus’s worst fears about the true nature of Peloria turned
out to be correct. Not long after the publication of his 1744 Peloria dissertation, someone,
perhaps another student, brought him yet another living specimen of Peloria. As Linnaeus
inspected it he realized, with a shock, that the plant contained both normal Linaria- type
flowers and Peloria- type flowers on the same inflorescence! According to the sexual system
of classification, this new specimen would simultaneously belong to two different classes,
an impossible situation! Years later Linnaeus’s son remarked that “after Peloria had fallen
short of his expectations [he] no longer wanted to hear any more said about this plant.”
Linnaeus clearly regarded his Peloria theory as his greatest blunder. In an essay published
in 1745, he referred readers to his dissertation on Peloria for “a stupid description” of this
pla nt’s va r ia bi l it y.^70
Linnaeus should not have been so hard on himself. The genetics, let alone the molecu-
lar biology, of species variability was totally outside the framework of eighteenth- century
natural history. We now know that Peloria is a variety of Linaria vulgaris that arises from