When WILHELM RUHLAND developed his plan for an Encyclopedia of Plant
Physiol- ogy more than three decades ago, biology could still be
conveniently subdivided into classical areas. Even within plant
physiology, subdivisions were not too difficult to make, and general
principles could be covered sufficiently in the two introductory volumes
of the Encyclopedia on the physical and chemical basis of cell biology.
But the situation changed rapidly even during the 12-year publication
period of the Encyclopedia (1955-1967). The new molecular direction of
genetics and structural research on biopolymers had an integrating
effect on all other biological fields, including plant physiology, and
it became increasingly difficult to keep previously distinct areas
separated. RUHLAND'S overall plan included 18 volumes and about 22,000
pages. It covered the entire field of plant physiology, in most cases
from the very beginning. But, as each volume appeared, it was clear that
its content would soon be outdated.