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classical explanation of pollen as a waste product. In direct contradiction to the results of
Camerarius, he regarded the male flowers of dioecious species as of no use to the flower.
In 1752, the German botanist Hans Möller, an asexualist critic of Bradley’s emasculation
experiments with tulips, wrote in the Hamburg Magazine that since anthers functioned in
excretion, which was required for purifying the sap, it was not the absence of pollination that
prevented seed production when the anthers were removed, but the presence of impurities
that could no longer be removed from the sap.^14 The question of how such a requirement for
waste excretion could possibly account for Camerarius’s results with dioecious plants, Möller
fails to address. To circumvent the problem of dioecious species, some asexualists resorted to
the equivocation that excretion was more important for some plants than for others.
One of the chinks in the armor of the sexual theory upon which asexualists pinned their
hopes was the existence of those few apparent exceptions, faithfully reported by Camerarius
(see Chapter 12), to the general rule that pollination was required for the production of
viable seed. According to Julius von Sachs, the importance of the exceptions was exagger-
ated in an abridged version of Camerarius’s results published later by his friend, Michael
Bernhard Valentin, Professor of Medicine at the Justus Liebig University in Giessen, to
whom Camerarius had dedicated De Sexu Plantarum. The asexualists were also unaware
that Camerarius had later shown that many dioecious species occasionally produce her-
maphroditic flowers, which could account for the small number of fertile seeds he found in
some of his isolated female plants.
Having read only Valintin’s abridged version of De Sexu Plantarum, Charles Alston,
Professor of Botany at the University of Edinburgh, therefore gained the erroneous impres-
sion that the experimental support for the sexual theory was weak. In 1754, Alston pre-
sented a dissertation in which he cited his own attempts to repeat Camerarius’s isolation
experiments with dioecious spinach, hemp, and dog’s mercury. Despite separating male and
female plants by seemingly insurmountable distances, he nevertheless reported obtaining
“good seeds” that germinated and produced normal male and female plants. Alston con-
sidered it highly improbable that the wind could have been involved, given the wind direc-
tion and the various barriers that insulated the plants. He also stated that he examined the
female plants and could find no stamens. “It therefore follows,” he concluded, “that the
liquor of the apices is not necessary for the fructification of plants.” As for the ancient claim
that female date palms require the dust from the male to bear fruit, he cited a contradictory
report by a gentleman named Labat:But Labat directly contradicts this doctrine by a fact. “We have,” says he, “a date tree
beside our monastery in Martinico, which carries ripe fruit though single, whether it
is a male or female I know not, but this I know for certain, that there was not another
kind within two leagues [six miles] of it.”Far from being a fructifying agent, Alston insisted, pollen was a waste product, and
“Nature has arranged for this dust to be thrown away as far as possible, for it is useless, if
not injurious to the style.”^15 The reason for Alston’s failure to repeat Camerarius’s results
is unclear. Perhaps experimental errors or errors in record keeping led him to obtain the
results he obviously desired. His ready acceptance of Labat’s anecdotal report suggests that
he was motivated to disprove the Linnaean system.