Preface: Working for many years with pines, I have been asked many questions I could not answer. Often I have thought how useful it would be for bothe the curious layman and the busy scholar to have assembled together as much information as possible on pines. Being a biologist, I am primarily interested in the biology of pines-their origin and development, their chemical composition, and their physiological processes. These considerations have naturally led me to the past and present distribution of pines. Difficulties of presenting these aspects of the subject are many The literature on pines is enormous; it is scattered through scientific, trade, and popular journals. What should be included and what omitted were not easy decisions. For instance, chemical components of pine and wood are considered; but physical properties of pine lumber are not, although there is a wealth of published information in that field. Keeping in mind the traditional remoteness of chemistry from plant taxonomy, I have perhaps oversimplified, in a conciliatory mood, the presentation of the chemical aspects of pines. On the other hand, I have attempted to make the presentation of taxonomy palatable to chemists, who are not always concerned with the ways and rules of classifying plants and are apt either to disregard accepted nomenclature entirely or to accept it in an amazingly uncritical manner. Our knowledge of the genus Pinus is rather uneven. Certain groups of chemical substances (polyphenols, terpenes) have been studies extensively; others, such as fats, are still known only sporadically. Alkaloids have been discovered in some pines only recently. Some physiological processes, such as mineral nutrition, have been investigated more thoroughly than others, for example, transpiration. Such unevenness will be noticed throughout the book. I have attempted to give ansers to many questions about pines; many have remained unanswered, and new ones have arisen. I have even attempted to offer some gerealizations and speculations, hoping that their presentation would not be condemned as heresy but, rather, would be accepted as a stimulus to more research along controversial lines. I have always been encouraged by Darwin's remark, in one of his letters to Wallace, that without speculation there would be no progress. N.T. Mirov--Berkeley, California, January, 1967.