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the existence of species comprised of separate fruit- bearing and pollen- bearing individuals,
such as date palms, willows, hops, nettles, spinach, and dog’s mercury. However, he added
the caveat that “this opinion concerning the use of pollen still requires confirmation.” Eight
years later, Ray seems to have dropped his earlier reservations. “In our opinion the pollen is
equivalent to the sperm of animals,” he wrote decisively, citing classical accounts of artificial
pollination in date palms as evidence. Shortly afterward, Ray reviewed an account, written
by the Italian botanist Paolo Boccone, of the Sicilian practice of artificial pollination in
pistachio trees.^32 Ray cited the practice as further evidence of the sexual role of pollen.
It is curious that neither Grew nor Ray ever thought to test the sexual role of pollen
experimentally. In the words of one historian, Grew’s “clear and useful account of structure
is sadly marred by guesses as to function and the propensity to put forth untested specu-
lations.”^33 But Grew, like Malpighi, was first and foremost a descriptive anatomist in the
tradition of Vesalius. Since he had access to the best microscopes available, and much of
what he described was new to science, it is not surprising that he dedicated the bulk of
his efforts to plant anatomy.^34 Nor did any other contemporary British botanists have the
time, resources, or motivation to test the new sexual theory of plants using the methodical
approaches of experimental natural philosophy. Those members of the Royal Society who
were in the best positions to test the new sexual theory of plants systematically showed no
inclination to do so. In Tübingen, however, there was a young physician named Rudolf
Jacob Camerarius who eagerly took up the challenge.Camerarius’s Scientific Influences
Rudolf Jacob Camerer (Latinized to Camerarius) was born in 1665 into a distinguished
family of doctors and apothecaries going back several generations.^35 His father was First
Professor of Medicine at the University of Tübingen. Rudolf attended the University of
Tübingen, earning his bachelor’s degree in Philosophy and Medicine in 1679, and his mas-
ter’s degree three years later. He subsequently entered medical school, working under the
supervision of Georg Balthasar Metzger, who was also Director of the University’s Hortus
Medicus. This garden had been established in 1663 by Duke Eberhard III of Württemberg,
and Metzger had become its Director in 1681.
After Camerarius completed his medical degree in 1685, he traveled throughout Germany,
Holland, England, France, and Italy for the next two years, returning to Tübingen in 1687,
on the eve of the War of the Grand Alliance.^36 While in England, Camerarius may have
paid his respects to his scientific idol, the British chemist Robert Boyle. Thanks to the
Royal Society of London, the experimental movement in Britain was flourishing. Boyle had
written voluminously on the limits of reason in comprehending Nature’s laws, which he
regarded as synonymous with God’s laws.^37 Boyle, a fervent Anglican who was also strongly
influenced by his sister’s Puritan convictions, believed, as did many of his fellow Society
members, that the experimental method was not only a tool for probing the laws of nature,
but a means to decipher the divine plan and thus to grow closer to God.
If Camerarius visited Boyle in England (the record is unclear), he likely would have borne
a letter of introduction from Johann Christoph Sturm (1635– 1703), theologian, natural phi-
losopher, and Professor of Mathematics at the University of Altdorf. Sturm had founded the