A sporangium diagram	Male reproductive "umbrella"
Female reproductive "umbrella"	Diagram courtesy The New York Botanical Garden

Class Hepaticae comprises the liverworts. These are small plants, no more than half an inch off the ground, that can be flat and ribbon-shaped or leafy. Liverworts grow close to the ground, and the sporophyte generation consists of a small stalk with a podlike capsule, the sproangium, on top. Most liverworts are diecious--they have both male and female reproductive units.

There are about 8,000 species of liverworts, which are abundant in rainforests and other moist areas across the world; they also inhabit a variety of other habitats, including polar and mild regions. Liverworts prefer to live in riverbeds, and some grow up the sides of tree trunks. It is believed that the liverworts evolved from algae before the mosses, and aided the first land colonization by amphibians by providing a sufficient amount of food.

There are two main groups of liverworts: the leafy liverworts, with about 80% of liverwort species, and the thallose liverworts. The leafy liverworts have leaf-like structres that grow in row patterns on branched or unbranched stems, usually with two rows of larger leaves and a single row of smaller leaves. Thallose liverworts, instead of a stem-leaf structure, consist of a flattened thallus. Both the leaves of the leafy liverworts and the thallus are only one to several cells thick.