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, — 



