Trace element science has undergone some dramatic changes in recent years and considerable discoveries have been made in the wide field of botany. This monograph reviews and summarizes the advances made in trace element research in botanical geography, taxonomy, phytocenology, geochemical ecology, morphology, anatomy, embryology and genetics.After a discussion of some general aspects of trace elements, the author makes a detailed critical analysis of their physiological role - a role that is not only of theoretical importance but one that can also provide a basis for the development of a rational system of plant nutrition. Various aspects of the problems dealt with, therefore, bear on practical issues in agriculture.