410 i Flora Unveiled
The same can be said for the botanical experiments of Lazzaro Spallanzini, the Italian
Catholic priest and experimental biologist who made important contributions to the
study of animal reproduction. Spallanzini was the foremost champion of the ovist camp
of preformationism in the eighteenth century. He was also the first to demonstrate that
physical contact with semen was required for the fertilization of an egg, in this case, a
frog egg. However, he concluded that it was the seminal fluid rather than the sperm that
effected fertilization.
Around 1777, Spallanzini attempted to test the sexual theory of plants but obtained
mostly negative results. In the cases of basil and dog’s mercury, he confirmed that the
“dust” was necessary for seed production, but he was unable to duplicate these results in
pumpkin, watermelon, hemp, or spinach. Julius von Sachs attributed Spallanzini’s fail-
ures to carelessness. According to Sachs, there was gossip at the time that Spallanzini’s
assistant had actually performed the experiments. Alternatively, Spallanzini’s error could
have resulted either from the presence of a few hermaphroditic flowers or from the rare
occurrence of parthenogenesis, termed apomixis, among some of his plants. Apomixis
occurs in about 0.1% of angiosperms, in more than 400 species belonging to 40 different
families. During apomixis, an embryo forms abnormally from a cell in the ovule other
than the egg cell. For example, during reproductive development in the monoecious vine
pumpkin (Curcurbita pepo), the plant undergoes a transition from male to female flowers.
According to geneticist G. Van Nigtevecht, this process culminates in the formation of
a parthenogenic female flower.^16 Such parthenogenic flowers can form fruits with viable
seeds in the absence of fertilization, which may have been the source of Spallanzini’s error.
If Spallanzini was misled by apomixis, his confusion about the requirement for pollina-
tion would be understandable.^17
On the other hand, François Delaporte favors the theory that Spallanzini may have
unconsciously misinterpreted his results to make them consistent with his ovist convic-
tions, which were strengthened by the recent discovery of parthenogenesis in aphids.^18 If he
had read Camerarius, however, he would have discovered that the young German botanist
had demonstrated the absence of preformed embryos in unfertilized ovules of bean plants.
Another prominent asexualist was William Smellie, a Scottish printer, editor, translator,
Professor of Natural History at Edinburgh University, and friend of Robert Burns. He was
also the author and compiler of the first edition of the Encyclopedia Britannica, which was
issued in installments between 1768 and 1771. In a discourse on the sexes of plants, Smellie
stated that as a young university student he had uncritically accepted the sexual theory,
having been misled by the “alluring seductions of analogical reasoning.” But, he states, after
“perusing Linnaeus and many other works on the subject” he was “astonished to find that
this theory was supported neither by facts nor arguments which could produce conviction
in even the most prejudiced minds.” Instead, “its principal support is derived from the many
beautiful analogies which subsist between plants and animals,” including the notion that
plant eggs must be fertilized by pollen to produce seeds. But, says Smellie, fertilization is
impossible in plants because the seeds have already acquired “bulk and solidity long before
the pollen, or supposed fecundating dust, is thrown out of its capsules.” Without providing
any evidence, Smellie asserts that seeds mature and develop hard seed coats before pollen
is shed from the anthers, making it impossible for pollen to make physical contact with