CHAP. I. 
REGULAR METAMORPHOSIS. 
539 
among roses than to find the ovaries converted into perfect 
leaves ; in such cases the margins uniformly occupy the place of 
the ovuliferous suture, and the midrib that of the sterile suture. 
But the most instructive and satisfactory proof of the pistil 
being merely a modified leaf, is to be found in the common 
double cherry of the gardens. In this plant the place of the 
ovary is usually occupied by a leaf extremely similar to those 
of the branches, but much smaller ; it is folded together ; its 
margins are serrated, and, in consequence of the folding, 
placed so as to touch each other ; and they occupy the place 
of the ovuliferous suture of a real pistil. The midrib of this leaf 
corresponds to the station of the sterile suture of the ovary, 
and is not only lengthened into a process representing a style, 
but is actually terminated by a stigma. I think, therefore, 
that all doubt as to the foliaceous nature of the pistil must 
cease. There is thus a greater identity of function between 
the pistil and the other series of the fructification than would 
at first appear probable. We seldom, indeed, find it con- 
verted into stamens ; but it often takes upon itself the form 
of petals, as has been shown above; and although cases are 
very rare of pistils bearing pollen, yet several instances are 
known of ovules being borne by the stamens. This occurs 
continually in Sempervivum tectorum ; I have shown it to 
happen in an Amaryllis, known in gardens as the double Bar- 
badoes lily (see the Horticultural Transactions^ vol. vi.) ; and 
it is constantly the case in a particular variety of the com- 
mon wall-flower, cultivated in the Apothecaries' Garden at 
Chelsea. 
We see then that there is not only a continuous uninterrupted 
passage from the leaves to the bracts, from bracts to calyx, 
from calyx to corolla, from corolla to stamens, and from sta- 
mens to pistil, from which circumstance alone the origin of all 
these organs might have been referred to the leaves ; but that 
there is also a continual tendency on the part of every one of 
them to revert to the form of leaf. Some botanists say, that 
all this depends upon an alternation of expansion and contrac- 
tion, which may be compared to the mechanical oscillation of 
the pendulum, and to the physical alternation observed in 
animated beings and the periods of life. The leaves, they 
