1840.] Remarh on the fruit of the Natural Order Cucurhitacecs. 45 



355. a. When the carpels are all distinct, or are separable with faci« 

 lity, they are apocarpous ; when they all grow into a solid body, which 

 cannot be separated into its constituent parts, they are syncarpous. 



356. The ovary is the lamina of the leaf. 



357. The style is an elongation of the midrib (174) 



358. The stigma is the denuded, secreting, humid apex of the midrib. 



359. Where the margins of the folded leaf, out of which the carpel 

 is formed, meet and unite, a copious developm.ent of cellular tissue 

 takes place, forming what is called the placenta. 



360. Every placenta is therefore composed of two parts, one of which 

 belongs to one margin of the carpel, and one to the other. 



36 1. As the carpels are modified leaves, they necessarily obey the 

 laws of arrangement of leaves, and are therefore developed round a 

 common axis. 



362. And as they are leaves folded inwards, their margins are neces- 

 sarily turned towards the axis. The placentse, therefore, being formed 

 by the union of those margins, will be invariably next the axis." 



From th's we learn, in few words, that the carpellary leaf is always so 

 folded that its midrib is towards the circumference, or forms the dorsum 

 of the cell or carpel, while the placentiferous margins are placed in the 

 axis ; that the difference between a on^-celled and many-celled fruit, 

 merely consists in the placentiferous margins of the carpellary leaves of 

 the former not extending inwards to the axis, but stopping in the cir- 

 cumference and bearing their ovules attached to the walls of the cell — 

 hence parietal. This position of the carpellary leaf is so constant, that 

 the possibility of an inversion of this order of things in a pepo seems 

 never to have entered into the calculations of any one of the numerous 

 botanists who have given their attention to the investigation of the 

 structure of this curious fruit ; and yet such is simply the case. In a 

 pepo the normal position of the midrib of the carpellary leaf is reversed, 

 that is, is plared in the axis, and the placentiferous margins towards the 

 circumference. That such is actually the case requires no argument to 

 prove ; we have only to cut the ovary of any true cucurbitaceous plant 

 to bo made sensible, at a glance, that it is so : though I confess that in 

 none have 1 seen it so clearly made out as in Coccinia Indica^ owing to 

 the carpels of that species remaining distinct, merely held together, not 

 as usual by cohesion between the respective carpels, but by the tube of 

 the calyx in which they are enclosed. Did I wish to illustrate the the- 

 ory by means of a diagram, I could not devise one more perfect than a 

 simple section of the ovary of that plant, merely extending the natural 

 divisions, by dividing the calyx, so as to allow each of the carpels to 



