Floral Evolution. 
377 
flowers with isomerous or oligomerous androecium. Indefiniteness 
in the latter is confined to a quite small group, the Ebenales ; while 
the ranalian type of flower, with indefiniteness in all the parts, 
elongated receptacle and apocarpous gyncecium does not occur 
among Sympetalse. The Archichlamydeae are considerably less 
advanced in regard to the Economy Principle than are the Sym- 
petalae ; and flowers with isomerous or oligomerous androecium 
coupled with a bicarpellary ovary are very rare indeed in the 
former series, 1 but very common in the latter. 
Again, the absence of any distinction between the essential 
organs of Archichlamydese and Sympetalae lends further weight to 
the probability that the two form a continuous series; we cannot 
say in any and every given case that a stamen or an ovary belongs 
necessarily to an archichlamydeous or a sympetalous flower. 
With regard to the evidence of the fossil record, this latter is 
so scanty in the matter of flowering plants that it may be employed 
only with the strictest caution. The evidence is necessarily of a 
negative character ; but, so far as it goes, it supports the view 
which we are endeavouring to maintain ; for the records of Archi¬ 
chlamydese are plentiful in strata geologically earlier than that 
containing the first remains of Sympetalse that have been discovered 
so far. Significant in the same connection is the fact that the 
Sympetalse with regular flowers are manifestly prior to the 
zygomorphic forms, according to the fossil record. 
Lastly, and perhaps the most significantly, the primordia of 
the corolla in Sympetalse, in so far as the facts of floral ontogeny 
have been investigated, are usually free in the inception of 
development; the corolla is rarely, if ever, laid down in a continuous 
ring. A glance through Payer’s Traite, frequently quoted in these 
chapters, will reveal this fact. The corolla makes its appearance in 
the form of separate papillae, which fuse at a very early stage. 
We conclude, then, that Sympetalse have been derived from 
polypetalous Dicotyledons; our examination of the several sympe¬ 
talous groups has been conducted on this assumption, and has led 
to results which may not be altogether unreasonable. 
We should, perhaps, mention that it is by no means impossible 
for a sympetalous group to have been derived directly from, say, 
a proangiospermous ancestry, without the intervention of a poly¬ 
petalous stock. A tubular perianth-whorl need not, of primd facie 
1 Apart from the exceptionally-advanced Umbelliferse, which are 
epigynous. 
