OF CEYLON AND INDIA. 
44 ^ 
fact that its degree seems to depend upon that of tlie vege- 
tative organs, and that it is never found without the latter, 
to say nothing of such difficulties as the erect position of 
most of the flowers and the apparent disadvantage of their 
dorsiventrality to them. 
It is evident that if this general contention be accepted as 
probable it opens up many new points of view, and many 
lines of research. There is as yet no evidence to show how 
the reaction affects the actual sporangia, the gametophyte, or 
the essential sexual generative cells ; the question requires 
investigation, in view of the fact that the lower groups of 
plants, from which ihe higher are supposed derived, are 
so largely dorsi ventral in structure. The general evidence 
above seems to indicate that in the higher plants the dorsiven- 
trality is derivative, and that radial structure has in general 
preceded it. 
If, now, we accept the dorsiventrality of the flower as in 
great degree the consequence of that of the vegetative organs 
— let the mechanism or correlation be what it may — we are 
led to some important deductions which once more raise 
several questions which have of late been formulated from 
other considerations, and which must be set at rest. 
If one character — or two, for suppression seems forced 
upon the flower of the Podostemaceæ as well as zygomor- 
phism — of great importance in morphology and taxonomy 
may thus be forced upon an organ without reference to its 
advantage or disadvantage in the performance of the func- 
tions of that organ, it seems only likely that other char- 
acters may have been forced upon the same or other organs 
in similar or other ways, and consequently that the study of 
adaptation must enter upon a new phase, or rather, must be 
accompanied and checked by the study of experimental and 
comparative morphology, and of variation and correlation, 
if we are to expect further valuable results. The study of 
correlation has already yielded many interesting facts, but 
in ontogeny rather than in phylogeny ; the case of the 
dorsiventrality of the flowers of the Podostemaceæ seems at 
( 59 ) 
