CHAP. II. OVARY. 169 



considerations : viz., that, as the carpels are modified leaves, 

 they are necessarily subject to the same laws of arrangement, 

 and to no others, as leaves developed around a common axis 

 upon one or several planes. For no axiom appears more in- 

 contestable in botany, than that all modifications of a given 

 organ are controlled essentially in the same way, and by the 

 same influences, as the organ itself in an unmodified state : 

 and hence every theory of the structure of fruit which is not 

 reducible to that which would be applicable to the structure 

 of whorls of leaves is vicious of necessity. I shall proceed to 

 demonstrate the perfect accordance of the carpellary theory 

 of structure in every point with these principles. 



The placenta arises from the two margins, either distinct 

 or more usually combined, of a leaf folded inwards. When 

 a leaf is folded inwards, its margins will point towards the 

 stem or axis around which it is developed ; and in a whorl 

 of leaves such inflected margins would all be collected 

 round a common centre ; or, if the axis were imaginary, 

 in consequence of the whorl being terminal, would be 

 placed next each other, in a circle of which tne back of the 

 leaves would represent the circumference. Therefore the 

 placentae will always be turned towards the axis, or will 

 actually meet there, forming a common centre ; and, which 

 is a very important consequence of this law, if one carpel 

 only, with its single placenta, be formed in a flower, the true 

 centre of that flower will be indicated by the side of the car- 

 pel occupied by the placenta. Proofs of this may be found 

 in every blossom: but particularly in such as, habitually 

 having but one carpel, occasionally form two, as the Wisteria 

 sinensis, Alchemilla arvensis, Cerasus acida, &c. ; in these the 

 second carpel, when added, does not arise by the side of the 

 first, but opposite to it, the face of its placenta being in front 

 of that of the habitual carpel. A fourth proof of this uniform 

 direction of the placentae towards the axis is afforded b}'^ 

 those pistils in which a great number of carpels is developed 

 in several rows, as in the Strawberry and the Ranunculus : 

 in all these the placentae will be, without exception, found 

 directed towards the axis, and consequently towards the 



