4X0 
The Ohio Naturalist. 
[Vol. XII, No. 2, 
Such a sequence can be traced more or less completely in other 
hydrophytic groups. 
Anemophily has also been developed independently in numer- 
ous groups; nearly always accompanied by the monosporangiate 
condition, loss of part or all of the perianth, and general reduction 
of the flower and the inflorescence. 
Peculiar morphological conceptions of . development are fre- 
quently formulated on the basis of an improper taxonomy, and 
transformations and re-creations are either tacitly or openly 
advocated, the acceptance of which would require a credulity 
greater than a belief in an innumerable series of special creations. 
Even the interpretation of the geological history of plants depends 
somewhat on our scheme of classification; since the geological 
history of plants, so far deciphered, is exceedingly incomplete 
and must still be interpreted through the morphology of living 
species. 
Three general systems of plant classification have been in 
vogue: (1) the artificial system, (2) the so-called natural system, 
and (3) the phyletic or evolutionary system. For the larger 
groups, the old natural system is still largely in use, and in the 
detailed arrangements of genera and species, one can still detect 
much of the artificial method. The natural system was not based 
on evolutionary principles, and probably prevented many of its 
followers from accepting the doctrine of descent because of the 
impossible transformations which would have been required to 
obtain genetic continuity in the series of plant forms expressed 
in the classifications of the time. 
To reconstruct classification on a phyletic basis will require 
much shifting, not only of the larger phyla and classes but also 
of orders, families, genera, and species. But we may safely 
formulate a principle of procedure which, although not always 
giving final results at present, will eventually lead to a true “nat- 
ural ’ ’ classification and will give us a more or less reliable present- 
ation of the evolutionary history of the plant kingdom. 
In tracing derivative relationships between two groups of 
plants, one of the essential considerations is the possibility of 
the transformation of the structures of the one into the other. 
Every morphological structure of the entire organism must be 
reasonably derived from some ancestral type, and the fact kept 
constantly in mind that one organ may be evolving or specializing 
rapidly while another is undergoing little change. In discussions 
of this nature carried on by those who do not follow the phyletic 
idea but divide plants arbitrarily by some more or less constant 
peculiarity, which may or may not indicate relationship, the 
result often becomes so artificial that whole groups of normal or- 
gans are derived bodily from the most extreme vestiges. So long 
as we do not see the course of evolution proceeding from vestigial 
