12 THE FOUNDATION OF ECOLOGY 
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 di- 
rected 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 devel- 
opment 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 an- 
cestral 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 con- 
tributing to a knowledge of evolution. The development of the latter has 
been greatly hindered by the dearth of actual facts, and by a marked ten- 
dency to compensate for this by verbiage and dogmatism. This is well illus- 
trated by the present position of the “mutation theory,” which, so far as the 
evidence available is concerned, is merely a working hypothesis. An in- 
credible 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. 
19. Taxonomy. Taxonomy is classified evolution. It is distinct from 
descriptive botany, which is merely a cataloguing of all known forms, with 
little regard to development and relationship. The consideration of the lat- 
ter is peculiarly the problem of taxonomy, but the solution must be sought 
through experimental evolution. The first task of the latter is to determine 
the course of modification in related forms, and the relationships existing 
between them. With this information, taxonomy can group forms accord- 
ing to their rank, i. e., their descent. The same method is applicable to the 
species of a genus, and, in a less degree, perhaps, to the genera which con- 
stitute a family. The use to which it may be put in indicating faimily re- 
