Volume 2 deals with the mechanisms of herbicide action and of resistance and tolerance to herbicides. The first five chapters of this volume cover the effects of herbicides and adjuvants on the physiology of plants. Professor Black‘s chapter begins by covering the effects of herbicides on photosynthesis, including photosynthetic assimilation of nitrogen, sulfur, and phosphorus. This is followed by Dr. Morelands chapter on herbicide interactions with plant respiration. The third chapter by Professor Bartels deals with the effects of herbicides on chloroplast and cellular development with emphasis on correlating physiological information with ultrasound effects.