OF CEYLON AND INDIA. 
449 
Indications are accumulating from many quarters, from 
palæobotany, from morphology, from the study of variation, 
and from other considerations, to show that the question of 
the possible polyphyletic origin of many groups hitherto 
supposed monophyletic, whether large species, genera, 
orders, or higher groups, is one which will soon demand 
much attention. Should this phenomenon prove to be at 
all common, it will of course explain many problems which 
have hitherto been great difficulties to students of evolution 
or taxonomy. 
All these suggestions of course contain a large element 
of speculation, but if we admit, and the evidence in its 
favour seems fairly strong, the first hypothesis, that the 
dorsiventrality (including suppression of organs, &c.) of 
the flowers, fruits, and seeds of the Podostemaceæ has been 
very largely determined by causes having nothing to do 
with their functions, while at the same time we regard these 
features of the floral structure as our great criteria in 
classification, all the questions above raised follow inevi- 
tably, and once raised on good evidence they must be settled 
one way or another before we can feel secure as to the 
stabilit}^ of the foundation upon which so imposing a structure 
has been raised in the sciences of biology. If we do not 
admit the hypothesis, we must find another which will as 
well explain the facts, themselves so striking that they 
demand explanation. 
It is clear that we require a detailed investigation of 
most of those comparatively constant structural features, 
especially in the floral organs, upon which we base our 
classifications, in order to discover among other things, 
whether, as seems to be the case in dorsiventrality, there 
is any correlation between them and any of the features 
of the vegetative system, or any other factors which may 
have been more or less causal ; any such correlation once 
traced or even imagined, the phenomenon should be the 
subject of physiological and experimental morphological 
investigation, as well as of variational studies. 
