Flora Unveiled

216 i Flora Unveiled

wisdom that plants obtained all their nourishment from the soil. He knew nothing about
photosynthesis— the fixation of carbon dioxide from the air in the presence of light. Because
plants seemed to absorb their food from the soil via their roots, Aristotle concluded that the
root performed the rudimentary functions of a mouth and digestive system. In contrast, the
plant’s reproductive structures, fruits and seeds, were located at the top of the plant rather
than the bottom. He therefore concluded that plants were analogous to upside- down animals.

Aristotle on “Generation” in Plants

Aristotle recognized two types of generation in biological organisms. In the usual case,
plants and animals arose from pre- existing plants and animals. However, some organisms
were thought to arise by “spontaneous generation” from decaying organic matter, such as
dung, forest litter, and rotting garbage, as in the cases of certain insects and seeds.^16 The
theory of spontaneous generation persisted well into the nineteenth century, until Louis
Pasteur’s sterilization experiments in 1859 finally disposed of it.
Among the animals that arose from pre- existing animals, Aristotle contrasted those that
move with those that do not move, such as barnacles, sponges, and other marine inverte-
brates, “which live by clinging to something else.” Animals that move have two sexes and
reproduce by copulating. The complementary roles of the sexes during copulation defines
which animal is male and which is female:

For by a male animal we mean that which generates in another, and by a female that

which generates in itself.^17

Nonmoving animals, on the other hand, reproduce without copulation. According to
Aristotle, such animals resemble plants both in their lack of motility and in the absence of
sexual reproduction:

But all those creatures which do not move ..., inasmuch as their nature resembles

that of plants, have no sex any more than plants have, but as applied to them [plants]

the word is only used in virtue of a similarity and analogy. For there is a slight distinc-

tion of this sort, since even in plants we find in the same kind some trees which bear

fruit and others which, while bearing none themselves, yet contribute to the ripening

of the fruits of those which do, as in the case of the fig tree and the caprifig.^18

Here, Aristotle admits that in the case of the fig and the caprifig there is “a slight distinc-
tion of this sort” resembling the two sexes of animals, but in actuality the caprifig is merely
hastening the ripening of the edible fig by supplying it with heat,^19 not by copulating with
it. In this passage, Aristotle seems to imply that plants are asexual.

However, Aristotle was clearly dissatisfied with his characterization of plant repro-

duction as asexual. Greek philosophers generally preferred principles that were both

simple and universal. Aristotle was therefore reluctant to make an exception to the

general rule of sexual reproduction in the case of plants. Thus he adopted Empedocles

view that plants do, in fact, have two sexes— but they are “mingled”: In all animals