The phase of experimental ecology which has to do with the plant has well been called experimental evolution. While this is a field almost wholly without development at present, there can be little question that it is to be one of the most fertile and important in the future. Attention will be directed first to those forms which are undergoing modification at the present time. The cause and direction of change will be ascertained, and its amount and rapidity measured by biometrical methods. The next step will be to actually change the habitat of representative types, and to determine for each the general trend of adaptation, as well as the exact details. By means of the methods used and the results obtained in these investigations, it will be possible to attack the much more difficult problem of retracing the development of species already definitely constituted. This will be accomplished by the study of the derived and the supposed ancestral form, but owing to the great preponderance of evolution over reversion, the study of the ancestral form will yield much more valuable results. The general application of the methods of experimental ecology will mark a new era in the study of evolution. There has been a surplus of literary investigation, but altogether too little actual experiment. The great value of De Vries’ work lies not in the importance of the results obtained, but in calling attention to the unique importance of experimental methods in contributing to a knowledge of evolution. The development of the latter has been greatly hindered by the dearth of actual facts, and by a marked tendency to compensate for this by verbiage and dogmatism. This is well illustrated by the present position of the “mutation theory,” which, so far as the evidence available is concerned, is merely a working hypothesis. An incredible amount of bias and looseness of thought have characterized the discussion of evolution. It is earnestly to be hoped that the future will bring more work and less argument, and that the literary evolutionists will become less and less reluctant to leave the relative merits of variation and mutation to experiment.