Flora Unveiled

420 i Flora Unveiled

Koelreuter’s Other Discoveries

In the course of his crossing experiments, Koelreuter also discovered the phenom-
enon of “hybrid vigor,” or heterosis. For example, he noted that hybrid Dianthus
plants had “increased vegetative power” compared to their parental stock, even
though they were self- sterile. He was quick to see the potential of the phenomenon
for agricultural improvement and thought it would be most beneficial for the breed-
ing of trees:

I would wish that I  or somebody else would be so lucky someday to produce a spe-

cies hybrid of trees which, with respect to the use of its lumber, would have a large

influence on the economy. Among other good properties such trees might perhaps

also have the one that they would reach their full size in one half the time of normal

trees.^30

Arguably, Koelreuter’s most influential work was on insect pollination and the adapta-
tions of flowers that facilitate interactions with insects. Since the time of Aristotle, it was
known that flowers provided food for bees, which feasted on nectar and pollen. In addition,
bees converted nectar to honey, thus indirectly providing nourishment for people. Philip
Miller had noted the role of bees in pollination, but it was Koelreuter who advanced the
fundamental ecological argument that the primary function of the floral nectaries was to
attract insect pollinators:

I was astonished when I first made this discovery, that the reproduction of plants is

a matter of chance, a lucky accident. But astonishment changed to admiration of the

method— at first sight accidental, but in fact certain— used by the wise Creator to

ensure their reproduction. To be sure, all the movements of these little servants of

nature show that, when they visit the flowers, they have nothing less in mind than

the execution of such an important task. But what does this matter? It is enough,

that without knowing it they undertake this all- important job for their own benefit

as well as for that of the plants. Their needed sustenance, little drops of sweet liquid,

lies hidden inside of these flowers. It requires effort and work to collect it; and in their

various movements, it happens that they brush off onto the stigmas the pollen which

they so easily had amassed on the hairs of their bodies to which it so readily clings.^31

Unlike Camerarius, Koelreuter received many accolades in his lifetime.^32 Three plant
genera were named in his honor, and he was elected to numerous scientific academies
and societies. Albrecht von Haller, who was a preformationist, had become aware of
Koelreuter’s publications even before they were published and quickly spread the news to
other prominent naturalists. Both the asexualist Spallanzini and the sexualist Erasmus
Darwin cited Koelreuter, and the German botanist Johann Hedwig, the first to describe
male and female reproductive structures in nonseed plants (cryptogams), declared in
1798 that Koelreuter had demonstrated “beyond all doubt” that “propagation by sexual
union takes place in the plant world also.” Koelreuter’s studies on insect pollination
strongly influenced both Christian Konrad Sprengel and Charles Darwin. Indeed, after
Koelreuter, the asexualist movement could no longer claim any scientific legitimacy.