=183. Scope.= The primary task of experimental evolution is the detailed study, under measured conditions, of the origin of new forms in nature. As a department of botanical research that is as yet unformed, it has little concern with the host of hypotheses and theories which rest merely upon general observation and conjecture. A few of these constitute good working hypotheses or serve to indicate possible points of attack, but the vast majority are worthless impedimenta which should be thrown away at the start. It is the general practice to speak of evolution as founded upon a solid basis of incontestible facts, but a cursory examination of the evidence shows that it is drawn, almost without exception, from observation alone, and has in consequence suffered severely from interpretation. With the exception of De Vries’s work on mutation, sustained and accurate investigation of the evolution of plants has been lacking. As a result, botanical research has been built high upon an insecure foundation, nearly every stone of which must be carefully tested before it can be left permanently in place. In a field so vast and important as evolution, experiment should far outrun induction, and deduction should enter only when it can show the way to a working hypothesis of real merit. The great value of De Vries’s study of mutation as an example of the proper experimental study of evolution has been seriously reduced by the fact that the “mutation theory” has carried induction far beyond the warrant afforded by experiment. The investigator who plans to make a serious study by experiment of the origin of new plant forms should rest secure in the conviction that the most rapid and certain progress can be made only by the accumulation of a large number of unimpeachable facts, obtained by the most exact methods of experimental study. The general application of field experiment to evolution will render the current methods of recognizing species quite useless. It will become imperative to establish an experimental test for forms and species, and to apply this test critically to every “new species.” Descriptive botany, as practiced at present, will fall into disuse, as scientific standards come to prevail, and in its place will appear a real science of taxonomy. In the latter the criteria upon which species are based will be obtained solely by experiment.