Types of Ovules

Anatropous

This is the most common type of ovule in angiosperms in which the ovule undergoes curvature such that the micropylar end comes to lie parallel to the funiculus.

Orthotropous

In this type of ovule no curvature occurs and the micropyle lies in a straight line with respect to the funiculus.

Hemi anatropous

The hemi anatropous condition results from the curvature of the ovule such that the micropyle comes to lie at right angles to the funiculus.

Campylotropous

In campylotropous type, the ovule is curved but the curvature is less than that in the anatropous condition.

Amphitropous

The amphitropous ovule looks like the campylotropous ovule at the first glance. But there is a point of distinction. In this type the nucellus and the embryo sac are curved like a horse shoe.

Circinotropous

Besides the above basic forms, another interesting type that you should know is the circinotropous ovule. In the early developmental stages of such ovules the .nucellar protuberance is more or less in line with the axis. In the further developmental stages, due to unilateral growth, it assumes anatropous form. The curvature does not stop at this, but continues until the ovule has turned over completely so that the micropylar end again points upwards. This kind of ovule is common in families Cactaceae and Plumbaginaceae.