CHAP. II. 
OVARY. 
167 
writings of Wolff, until the admirable Treatise upon Vege- 
table Metamorphosis, which had been published by Goethe 
in 1790, but which had long been neglected, was again 
brought into notice, and illustrated by the skilful demonstra- 
tions of De Candolle, Turpin, Du Petit Thouars, and others. 
121 122 
According to these writers, the pistil is either the modifi- 
cation of a single leaf, or of one or more whorls of such leaves, 
which are technically called carpels. Each carpel has its own 
ovary, style, and stigma, and is formed by a folded leaf, the 
upper surface of which is turned inwards, the lower outwards, 
and the two margins of which develop one or a greater num- 
ber of buds, which are in a rudimentary state, and are called 
the ovules. 
A very distinct idea of the manner in which this occurs 
may be obtained from the carpel of a double cherry, in which 
the pistil loses its normal carpellary character, and reverts to 
the structure of the leaf. In this plant the pistil is a little 
contracted leaf, the sides of which are pressed face to face, 
the midrib elongated, and its apex discoloured, or a little dis- 
tended. If we compare this with the pistil of a single cherry, 
the margins of the leaf with the ventral suture, the elongated 
midrib with the style, the discoloured distended apex with the 
stigma, they will be found to correspond exactly. 
In this case there is an indisputable identity of origin and 
nature between the ovary and the blade of a leaf, — between 
the little suture that occupies one angle of the carpel of a 
cherry, and the line of union of the two edges of the leaf, — 
M 4 
