168 
ORGANOGiTAPHY. 
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 which 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 syncarpous. 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 
pistil as that of Nigella damascena. 
This important conclusion is dediicible fron^ the foregoing 
