This study of plant anatomy is based on newly available data on the structure and spatial organization of the vascular system of plants. For the first time, by means of a new technique of intracellular moulding, the vascular system can be observed in its length. Many examples are chosen from among the major groups of the plant kingdom to illustrate the vast field of applications of histological moulding: anatomical structures that have so far been little understood or unknown are described and hypotheses relative to the cambial functioning are presented. Following a summary of basic concepts of xylem anatomy, the text is illustrated with many diagrams and photographs of moulds made for the most part with scanning electron microscope. The successive steps of the technical implementation of moulding, are described with precision. The book is addressed not only to scientists and students, but also to professionals concerned with wood, trees, and plants in general.