Placentation
It is the arrangement of ovules in an ovary.
When the gynoecium is monocarpous, the placentation can be marginal or basal.
When the gynoecium is syncarpous, the placentation can be axile, parietal and free central.
(a) Marginal placentation
The placenta appears as one ridge on the ovary wall and ovules are attached to the placenta in a row e.g. beans in a pod.
(b) Basal placentation
The placenta is formed at the base of ovary with ovule(s) attached to it e.g. sunflower, mango.
(c) Parietal placentation
The edges of the carpels fuse together and the dividing walls disappear, leaving a loculus.
Placenta of each carpel appears as ridges on ovary wall with numerous ovules on them e.g. pawpaw.
(d) Axile placentation
The edges of the carpels fuse together to form central placenta in the axil formed the carpels.
Ovules are arranged on the placenta.
The ovary is divided into a number of loculi by the walls of the carpel e.g. orange.
(e) Free central placentation
The edges of carpels fuse together and the dividing walls disappear leaving one loculus e.g. primrose.
A placenta appears at the centre of the ovary and has numerous ovules on it.
