R. P. PHARIS and D. M. REID The idea of a separate Encydopedia volume dealing with the "interrelations of plant hormones with factors in the environment of the plant, and its organs and tissues" originated with N. P. KEFFORD, and we are most appreciative of the help and advice provided by Prof. KEFFORD in the formative stages of this volume. We have thus interpreted "environment" very broadly to indude not only factors external to the plant, e. g. , gravity, light, temperature, wind, mechanieal wounding, water, organism s (induding pollen), and magnetic and electric stimuli, but internaI factors as well (e. g. , nutrients, both inorganic and photoassimilate, direction, and time). In our definition of "hormonaI effect", or "hormonaI involvement", we have asked our authors to take a broad ap proach, and to examine not only phenomena that are mediated by the known plant hormones, but to discuss as well a wide variety of processes and events where hormonal involvement is implied through more indirect analyses and observations. The volume begins with environmental factors internaI to the plant; R. J. WEAVER and J. O. JOHNSON thus examine "hormones and nutrients", their inter relationship in movement, accumulation, and diversion. As one studies a plant during its rapid growth phase, and later as maturation and aging proceed, it becomes apparent that time is an environmental cue of great significance, one which may exert a major influence via hormonal messages.

I: Factors Internal to the Plant

Nutrients
1 Relation of Hormones to Nutrient Mobilization and the Internal Environment of the Plant: The Supply of Mineral Nutrients and Photosynthate
Time-Related Factors and Phenomena
2 Rhythms and Their Relations to Hormones
3 Hormonal Aspects of Phase Change and Precocious Flowering
Direction
4 Polarity
5 Epinasty, Hyponasty, and Related Topics
6 Position as a Factor in Growth and Development Effects
II: Factors External to the Plant Gravity
Gravity
7 Roles of Hormones, Protons and Calcium in Geotropism
Light
8 De-Etiolation and Plant Hormones
9 Photoperiod and Hormones
10 Roles of Hormones in Phototropism
Temperature
11 Plant Growth Regulators and Low Temperature Stress
Wind and Other Mechanical Factors
12 Wind and Other Mechanical Effects in the Development and Behavior of Plants, with Special Emphasis on the Role of Hormones
13 Hormonal Control of Wound-Induced Responses
14 Water Relations and Plant Hormones
Organisms
15 Pollen. Symbionts and Symbiont-Induced Structures
16 Pathogenic and Non-pathogenic Microorganisms and Insects
17 Electrical and Magnetic Stimul
18 Regulators of Plant Reproduction, Growth and Differentiation in the Environment
Hormones and Plant Ecology
19 The Ecological Role of Plant Growth Substances
Author Index.