In recent years, molecular biology has infiltrated into all branches of botany. This is particularly true of plant physiology. This book attempts to provide an introduction to the metabolic and developmental physiology of higher plants from a molecular biological point of view. Starting from the heterocatalytic function of DNA the first ten chapters deal with metabolism; development is presented in the last nine, starting from the autocatalytic functions of DNA and including certain topics oriented more toward metabolic physiology. Both fields of plant physiology are so closely linked that an in tegrated presen tation of this kind seemed not only possible but desirable. In contrast to other accounts, an attempt has been made to give equal weight to metabolism and development. In particular, the so-called "sec ondary" plant materials, which are of considerable interest to the phar macist, the nutrition technologist, the plant breeder, and the agriculturalist, as well as to the biologist, are treated sufficiently. It is ob vious that the wealth of material made an illustrative style of presentation necessary. The book is intended for beginners, and so it has had, in part, to be simplified. Even so it has not been possible to write it without mentioning hypotheses that anticipate much more research. The beginner ought also to learn how working hypotheses are first postulated on the basis of cer tain facts and then must either be proved or refuted.