OVARY AND PLACENTA
The Ovary encloses ovules. These are structures that contain eggs which, after fertilisation, will develop into seeds. The ovules are attached to a part of the ovary known as the placenta and this is where the pollen tube enters the ovule during the process of fertilisation. The stalk that attaches the ovule to the placenta is called the funiculus. The ovary may have one or more chambers. These are known as locules. The ovary may have a single locule (unilocular) or may be divided (multilocular). Each locule may have one or more ovules. The compartments are separated by walls called septa. The arrangement of placentas in the ovary is termed placentation. There are several types.
A placenta can form at the base or apex of a single locule and this is termed basal or apical placentation. Other types of placentation are:-
marginal placentation. Ovules attache to the wall of an elongated ovary along its ventral suture, also known as its margin as in the Pea family, Leguminosae.
free-central placentation. Ovules attach to a central column as in the Pink family, Caryophyllaceae.
axile placentation. Ovules attach to the central axis of a multilocular ovary as in the daffodil
parietal placentation. Ovules attach at several points on the wall or outgrowths from it, as in the Poppy family, Papaveraceae. Parietal means ‘of a wall’.