172 BOTANICAL GAZETTE [SEPTEMBER 
of the world. In accordance with it we may explain m a good degree the 
present distribution of species and other groups over the world. It rationally 
connects the order of the appearance of vegetable types in time with the 
grades of differentiation and complexity, both proceeding from the simpler, or 
lower and more general, to the higher and more differentiated or special; it 
explains by inheritance the existence of functionless parts; throws light upon 
the anomalies of parasitic plants in their various gradations, upon the assump- 
tion of the most various functions by morphologically identical organs, and 
indeed illuminates the whole field of morphology with which this volume has 
been occupied. It follows that species are not ‘‘simple curiosities of nature,” 
to be catalogued and described merely, but that they have a history, the rec- 
ords of which are impressed upon their structure as well as traceable in their 
geographical and paleontological distribution.” 
In an adjoining paragraph he tersely sums up the matter in 
this aphorism : 
Affinity under this view is consanguinity, and classification, so far as it is 
natural, expresses real relationship. 
We are warranted in strenuously urging a conformity of 
taxonomy with phylogeny, and while we must be cautious not 
to propose a new arrangement for every phylogenetic vagary 
which may arise, we must be equally careful not to allow our 
natural inertia, or the conveniences of the art of botany, to 
retard any change demanded by science. 
Four years ago I discussed** the insufficiency of the Can- 
dollean system, and a year ago that of the system of Engler 
and Prantl"’ as expressions of genetic relationship. Further 
study of the problem and of these systems has deepened my 
conviction that while each is doubtless the best formula of the 
results of its period, neither one is today an adequate expression 
of our knowledge of the structure and relationship of the 
angiosperms. We are not to imagine, however, that the work 
of the past is to be thrown aside as worthless, and that the sys- 
tem based upon phylogeny will have nothing in common with 
the older systems. On the contrary, when examined critically, 
35tructural Botany 330. 
™ Evolution and classification. Proc. A. A. A. S. 42: 237. 
*s The point of divergence of monocotyledons and dicotyledons. Bor. Gaz. 22: 
