CHAP. II. 
OVARY. 
207 
Such is the structure of an ovary in its most common state ; 
certain deviations from it remain to be explained. We have 
seen that when carpels become syncarpous, they form a pistil, 
the ovary of which has as many cells and dissepiments as there 
are carpels employed in its construction. But sometimes the 
united sides of the carpels do not project so far into the cavity 
of the ovary as to meet in the axis ; and then the result is an 
ovary, which, although composed of many carpels, is never- 
theless one-celled [fig* 132.). In such case the dissepiments 
project a short distance only beyond the inner lining, or 
paries, of the ovary, and, bearing on their edges the placentae, 
the latter are said to be parietal. In other plants, such as 
Corydalis, Viola, and Orchis, the carpels are not folded 
together at all, but are spread open and united by their edges 
(fig* 133.): in that case the placentae do not project at all 
into the cavity of the ovary, but are still more strictly parietal 
than the last. 
132 133 134 
Another class of anomalies, of a still more remarkable cha- 
racter, is that in which there are no dissepiments, while the 
placentae form a distinct mass in the centre of the ovary, 
as in Lychnis ; this is what is called a free central placenta 
[fig. ]34.). But, if we examine these plants at a very 
early period of their formation, long before the flowers 
expand, the explanation of the anomaly is sometimes not 
difficult. It will be found that such plants as Alsinaceae 
have, at that time, their dissepiments meeting in the centre, 
and forming there a fungous placenta ; but subsequently the 
shell of the ovary grows more rapidly than the dissepiments, 
and breaks away from them; while the excessive growth of 
the placenta afterwards destroys almost all trace of them : 
their previous presence is only to be detected by lines upon 
