The professional forester is not so much concerned with pure taxonomy as with applied taxonomy. He has consequently tended to regard the rules of botanical nomenclature as falling outside his province and has usually left the field of pure taxonomy to the botanist. The forester's main objects have been to avoid ambiguity in nomenclature and confusion in his records, so that he requires that each kind of tree should bear a name which is universally applicable from the scientific and legal point of view and that nomenclature should acquire stability. In recent years, however, he has been called upon to accept so many changes in familiar names that he may be forgiven for wondering whether either object is feasible of attainment. It is with the purpose of demonstrating that the botanist is fully alive to the requirements of the forester and has his interests at heart that we present the following popular account of the steps the botanist has taken to secure the universal applicability and eventual stability of nomenclature. It will be seen that change and alteration are inevitable stages in the progression towards ultimate stability. This article was conceived in the course of discussions between the late John Turnbull and the author. The latter, although formerly a professional botanist and still intensely interested in botany, is now very fully occupied in other spheres. We are thus greatly indebted to Mr. Turnbull for persuading Mm to devote so much of his time to its preparation. We believe that his style of presentation and numerous examples will interpret many technicalities for readers who in the main will regard themselves as laymen in this subject.—(Ed.)