168 ORGANOGRAPHY. BOOK I. 



and between the elongated midrib, with its distended apex, and 

 the style and stigma. There can be no doubt that the plan 

 of all carpels is the same ; so that the ovary is the blade of a 

 leaf, the style an elongated midrib, and the stigma the denuded, 

 secreting, humid apex of the latter. 



Such being the origin of the carpel, its two edges will cor- 

 respond, one to the midrib, the other to the united margins of 

 the leaf These edges often appear in the carpel like two 

 sutures, of which that w^hich corresponds to the midrib is called 

 the dorsal, that which corresponds to the united margins is 

 named the ventral suture. 



It is at some point of the ventral suture that is formed the 

 -placenta, which is a copious development of cellular substance, 

 out of which the ovules or young seeds arise. It, the placenta, 

 originates from both margins of the carpellary leaf; — but, as 

 they are generally in a state of cohesion, there appears to be 

 but one placenta, — nevertheless, if, as sometimes happens, 

 the margins of the carpellary leaf do not unite, there will be 

 two obvious placentae to each carpel. Now, as the stigma is 

 the termination of the dorsal suture, it occupies the same 

 position as that suture with regard to the two placentae ; con- 

 sequently the normal position of the two placentae of a single 

 carpel will, if they are separate, be right and left of the 

 stigma. This is a fact very important to bear in mind. 



Pistils consisting of but one carpel are simple; of several, 

 are compound. If the carpels of a compound pistil are dis- 

 tinct entirely or in part, they are apocarpous, as in Caltha; if 

 they are completely united into an undivided body, as in 

 Pyrus, they are sj/ncarpous. That syncarpous pistils are really 

 made up of a number of united carpels is easily shown, as 

 Goethe has well remarked, in the genus Nigella, in which N. 

 orientalis has the carpels partially united, while N. damascena 

 has them completely so. In the latter case, however, the styles 

 are distinct; they and the stigmas are all consolidated in a 

 single body, when the pistil acquires its most complete state 

 of complication, as in the Tulip; which is, however, if care- 

 fully examined, nothing but an obvious modification of such a 

 })istil as that of Nigella damascena. 



This important conclusion is deducible from the foregoing 



