Trees have the distinction of being the largest and oldest living organisms on earth. Although the herbaceous habit has made unprecedented evolutionary gains since the middle and late Cenozoic, trees still are the most conspicuous plants covering the habitable land surface of the earth. Man has long sought their shelter and protection, utilized their food and fiber, and often exploited them to his own detriment. Trees have always been of much interest to botanists, and many of the early investigations concerning the structure and function of plants were conducted with trees. At the beginning...

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...