282 KINDS OF PLACENTATION. 
1. Kinds of Placentation.—In the simple ovary the placenta 
is always situated at the ventral suture or that point which 
corresponds to the union of the two margins of the blade of 
the carpellary leaf (figs. 585, 586, and 628), out of which it is 
formed ; such a placenta is therefore usually termed marginal, 
or sometimes axile from its being turned towards the axis of the 
plant. The latter term is better reserved for the placentation 
of certain compound ovaries, as described below. 
In compound ovaries we have three kinds of placentation ; 
namely, awile or central, parietal, and free central. The amile or 
central occurs in all compound many-celled ovaries, because in 
these each of the ovaries of the component carpels is placed in 
a similar position to that of the simple ovary (figs. 612 and 613), 
and hence the placentas situated at their ventral sutures will be 
arranged in the centre or axis, as in the Lily (fig. 629), and 
Campanula (fig. 630). By many botanists this mode of placen- 
Fic. 629. Fic. 630. 
Fig. 6381. 
: _ Poa 
Fiy. 629. Transverse section of the compound ovary of the Lily. The ovary 
is three-celled (trilocular). The placentas, p/, are axile or central. 
Fig. 630. Transverse section of the ovary of a species of Campanula. The 
ovary is five-celled or quinquelocular, and the placentation, pl, axile or 
central. Fig. 631. Transverse section of the ovary of aspecies of Cactus. 
The oyary is one-celled and the placentation parietal. 
tation is called central, and the term awile is restricted to the 
form of placentation where the placenta is supposed to be a 
prolongation of the axis. This will be afterwards alluded to 
(page 285). 
In a compound one-celled ovary there are two forms of pla- 
centation, namely, the parietal, and the free-central. The pla- 
centation is termed parietal, when the ovules are attached to 
placentas either placed directly on the inner wall of the ovary, 
as in the Mignonette (fig. 621, pl), and Cactus (jig. 631); or upon 
incomplete dissepiments formed, as already noticed, by the par- 
tially infolded ovaries, as in the species of Orchis (fig. 622, pl) 
and Poppy (fig. 623, plac). In parietal placentation, the number 
of placentas corresponds to the number of carpels of which the 
ovary is formed. When the placentas are not attached to the 
inner wall of the ovary, but are situated in the centre of the 
cavity and perfectly unconnected with the wall, they form what 
