41 o 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 indeiDcndently in numer- 

 ous groups; nearl}^ always accompanied by the monosporangiate 

 condition, loss of part or all of the perianth, and general reduction 

 of the flower and the inflorescence. 



Peculiar morj^hological conceptions of development arc 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 fomis 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 possibilit}^ of 

 the transformation of the structures of the one into the other. 

 Every morphological structtire 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 bodil}' from the most extreme vestiges. So long 

 as we do not see the course of evolution proceeding from vestigial 



