Flora Unveiled

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combined with reason and logic were the most reliable guides to truth. In his treatises on

animals, Aristotle referred to other works he had written about plants, but these, unfor-

tunately, have been lost. However, we can reconstruct Aristotle’s general thoughts about

plants from the frequent references to them in his writings about animals. Most of his ideas

about sex in plants can be found in De Generatione Animalium.

Aristotle defined four essential life processes: nutrition, growth, movement, and feeling.

By “movement,” Aristotle meant not only kinetic movement through space, but also the

changes in shape brought about by development. “Feeling,” according to Aristotle, included

both “thinking” and “desiring” in addition to “sense perception.” The possession of any one

of these four functions was indicative of life, but the highest category of living beings pos-

sessed all four. Plants were included among living beings because they had the properties of

nutrition, growth, and movement (development), but were lower than animals because they

lacked feeling. The idea that plants lacked feeling contradicted Empedocles, who attributed

“strife” and “love” to everything in the universe, including plants and minerals.

According to Aristotle, all living things possessed a soul. The soul was thought of as the

indivisible essence of the organism and the source of “the powers of self- nutrition, sensation,

thinking, and motility.” Plant souls, however, were only capable of self- nutrition.

Reasoning that the soul is required by every part of the body, Aristotle inferred that it

must be present throughout the entire organism. He then posed the question: “Is each of

these a soul or a part of a soul?” To Aristotle, the fact that the higher animals die when cut

in half suggested that they possess a single, large soul that is extinguished by division. Plants

and “certain insects,”^13 on the other hand, are able to survive being cut into segments, sug-

gesting that each of the segments contains its own soul:

It is a fact of observation that plants and certain insects go on living when divided

into segments; this means that each of the segments has a soul in it identical in species,

though not numerically identical in the different segments, for both of the segments

for a time possess the power of sensation and local movement.^14

Because plants can regenerate whole plants after being divided into segments, the single

soul of an individual plant must also be capable of forming multiple souls when cut into pieces:

[P] lants which when divided are observed to continue to live though removed to a

distance from one another ... show ... that in their case the soul of each individual

plant before division was actually one, potentially many.^15

As noted earlier, Aristotle also believed that living things were ordered from their

creation into a hierarchy, which in the Middle Ages came to be called the Scala Natura

(Ladder of Nature) or “Great Chain of Being.” Celestial beings— divine and therefore

perfect— occupied the uppermost rung, with people just below them. Large animals were

regarded as degenerate forms of humans, and smaller, simpler animals were degenerate

forms of the larger more complex animals. Plants were degenerate forms of the simpler

animals, and minerals were degenerate forms of plants.

Because Aristotle believed that humans represented the most perfect form of life on

earth, he assumed that it was possible to understand the biology of lesser animals and

plants by drawing analogies to humans. For example, Aristotle accepted the conventional