PLACENTATION

Placentation

The arrangement of the ovule in a ovary is known as placentation.

TYPES OF PLACENTATiON

On the basis of aarangement of the ovule in a ovary,  placentation will be five types.

1) Axile placentation
2) Parietal placentation
3) Free central placentation
4) Basal Placentation
5) Marginal placentation

1) Axile placentation

Here, the placenta develop from the central axis which correspond to the confluent margins of carpels. It occurs in bi-to multilocula Primerose.
e.g., Solanaceae, Malvaceae.

2) Parietal placentation

The word parietal is applied to the placentation in free carpal and is also applied to the type of placentation in the syncarpous ovary.
Parietal in its meaning on the walls. It applicable to both the sub marginal and laminal placentation, but this term parietal placentation resticated to syncarpous ovary.
Ex:- Mustard, Argemone

3) Free central placentation

Here, the placentae develop in the centre of the ovary as a prolongation of floral axis and the ovules are attached on this axis. It occurs in multicarpellary but unilocular ovary, e.g., Dianthus,  Primerose

4) Basal placentation 

It is a reduced type of placentation derieved from central placentation with the placenta reduced in size and the ovule is 1 single locule with one ovule.  One ovule present at the base of ovary.
Ex:- Compositae,  Amaranthaceae

5) Marginal placentation

The ovules develop in rows nears the margin on the placenta formed along the ventral suture. It occurs in monocarpellary and unilocular ovary.
e.g., Leguminosae.