Angiosperms

At the root of their diversification

Angiosperms developed from the Lower Cretaceous onwards (circa 120 Ma) and dominate present-day flora. They are termed “flowering plants” but are more precisely “flowering and fruiting plants” as they are the only plants to produce fruit.

Because of their mode of reproduction and their very diverse anatomical characteristics, angiosperms were able to colonise most environments on our planet from the beginning of the Cenozoic (circa 65 Ma).

Angiosperms

Plants with fruit

The ovules of angiosperms are enclosed within a fertile leaf called a carpel. Condensed within a single structure, stamens and carpels are enveloped by sterile parts that are actually transformed leaves. After pollination and fertilization the carpel produces the fruit. This description applies generally to hermaphrodite flowers; certain angiosperms, however, possess separate male and female flowers.

The most ancient angiosperm flowers are composed of isolated parts arranged along a stem. The most recent flowers are more condensed, surrounded by enveloping parts that form the calyx and corolla.

Angiosperms

Magnolia

Flowers with an archaic organization

Magnolia

And the profusion of forms

Among the angiosperms, the magnoliidae have flower parts that are arranged in a helix, harking back to an archaic structure.

Monocotyledons and eudicotyledons are distinguished by flowers arranged in successive cycles of equivalent parts: sepals, petals, stamens and carpels.

Angiosperm groups are differentiated not only by their anatomical characteristics but also by palynological characteristics (relating to pollen grains).