Floral Evolution. 
ii 7 
methods of its production may have been, the inferior position of 
the ovary conduces to economy in production, since, in virtue of 
this position, receptacular tissue can be pressed into the service of 
ovule-protection and of fruit-formation. In any case it is certain 
that those floral types, such as the Composite, which are admittedly 
in the van of evolutionary advancement, invariably possess an 
inferior ovary, while no epigynous flower can be called unquestionably 
primitive. 
We are now in a position to approach a study of the Sympetalae. 
The sole essential difference between the Archichlamydeze and the 
Sympetalae is that the corolla in the latter group is composed of 
united petals, while in the former the petals are free. 
We have attempted to portray the significance of this cohesion; 
its essence, in a word, is adaptation to insect-visits; and the 
formation of a corolla “ tube ” is at once the most elementary and 
the most extensively occurring structural device to this end. 
Now it is not to be supposed that this cohesion of petals 
followed upon one evolutionary line of descent only ; nor, further, 
that sympetaly originated at one point only—the terminal point— 
of any particular line. Thus, one main line in the Archichlamydese 
is determined by the principle of economy in the production of parts, 
traceable, first, in the reduction of the stamens to two whorls with 
obdiplostemonous arrangement, and, secondly, in the further 
reduction to one isomerous whorl, the corresponding members of 
corolla and andrcecium being placed, primarily, each opposite to 
the other, and secondarily, in an alternating arrangement. It is 
not reasonably to be anticipated that the tendency of progressive 
adaptation to insect visits would lag so far behind the principle of 
economy as to wait, if we may so express it, until an isomerous 
andrcecium was established before it produced a sympetalous 
corolla. Nor, indeed, is such the case; the Heteromerce, one of 
Bentham and Hooker’s three main divisions of the sympetalous 
Dicotyledons (corresponding to the Pentacyclidce of Engler), reflect 
the association of a sympetalous corolla with a double staminal 
whorl. In the Primulales, the stage at which the stamens are 
equal in number but opposite to the corolla segments, is represented. 
The Ebenales, again, are the sympetalous representatives of what 
we have designated the “secondary branching tendency,” with 
indefiniteness, typically, in all the the parts of the flower. 
