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The following year (1788) Sprengel made another important discovery: the positions of
colored spots on the petals of certain flowers often served as guides directing insects to the
nectaries:If the corolla has a particular color in particular spots ... it is for the sake of the
insects that it is so colored; and if the particular color of a part of the corolla serves
to show an insect which has lighted on the flower the direct path to the nectar, the
general color of the corolla has been given to it, in order that insects flying about in
search of their food may see the flowers that are provided with such a corolla from a
long distance, and know them for receptacles of nectar. ^45To Sprengel, such floral features designed specifically for insect pollinators provided
proof of God’s existence because it showed that even the tiniest, most inconspicuous struc-
tures of flowers had been created with a specific purpose in mind. At a time when the study
of natural history was still hampered by creationist ideas, Sprengel’s application of teleology
to virtually every visible structure of the flower opened the door to a series of important
discoveries in floral ecology.
Sprengel’s magnum opus was more than four hundred pages long and richly illustrated
with more than a thousand minutely detailed anatomical figures crammed into twenty- five
copperplates. These included analyses of 461 individual species of flowering plants arranged
in Linnaean taxonomic sequence. Each species was discussed according to its pollen vector
(insect vs. wind) and the floral mechanism for attracting insects and facilitating pollina-
tion. Since no one had ever done this before, Sprengel was in the enviable position of mak-
ing one discovery after another, laying the foundation for the new field of floral ecology.
Stefan Vogel at the University of Mainz has listed nine major findings in floral ecology and
fifteen additional insights into other important phenomena attributable to Sprengel.^46
Arguably, the most significant question Sprengel addressed was the source of the pol-
len that was ultimately deposited on the stigma by the pollinator. If, for example, a bee
simply transferred pollen from a flower’s anther onto the stigma of the same flower, the
bee would simply be facilitating self- pollination. If, on the other hand, the pollen that
the bee deposited on the stigma was derived from a different flower, the bee would be car-
rying out cross- pollination or “out- crossing.” Sprengel realized that, in the case of dioe-
cious species, outcrossing was the rule, and it was also common in monoecious species
such as maize. However, it had long been assumed by Sprengel and his contemporaries
that all hermaphroditic flowers, which make up more than 85% of flowering plants, were
self- pollinating. Self- pollination seemed to Sprengel, as it did to Koelreuter, the logical
mechanism, designed by the wise Creator to prevent mixing and to assure the fixity of
species. Thus he was surprised to discover features of flower morphology that seemed to
prevent self- pollination, such as dichogamy, in which the stamens and pistils of the same
flower mature at different times, thereby preventing self- pollination.^47 Sprengel drew the
counterintuitive conclusion that “nature does not seem to allow any flower to be fertil-
ized by its own pollen.” Insect- mediated pollination, according to Sprengel, causes out-
crossing, not self- pollination.
Even Sprengel was troubled by such a radical idea, which flew in the face of the con-
ventional wisdom that self- pollination was necessary to maintain the fixity of species.