Figure 8.5. The tea plant, Camellia sinensis, native to East Asia.
Most of the strange molecules found in plants have not been
carefully investigated for the physiological effects they may cause.
Thus, the effect of any plant, when ingested, will be a complex combi-
nation of many things. We may be able to attribute a substantial part
of the plant’s effect on physiology and behavior to a single molecular
entity, but the overall effect will necessarily be more complex (and
interesting) than that. Coffee, tea, cacao, yerba mate, guarana and kola
all contain caffeine, but all also differ in the effects they have on the
human psyche. And one kind of tea may be different in effect from an-
other kind of tea—even though all may contain caffeine and all come
from the same species of plant, Camellia sinensis (Fig. 8.5).
The history of drugs is mostly a history of ethnobotany, the study
of how people—over the course of millennia and continuing to this
day—have discovered and used the powers of plants. Long ago it was
appreciated that plants have powers and that among those powers are