Thallus means a sheet-like form which does not have any resemblance to typical plant organs like leaves, stems or roots. The thallose liverworts have thalli which resemble green algae. In some cases all of the cells contain chloroplasts and the marginal areas are only one cell thick. Some display Marginal Growth like Coleochaete and have Chloroplasts that are similar to the Green Algae (Chlorophyta).

Drawing of Anthoceros Thallus. The meristematic cells are located along the margins. This produces a flat, circular organism. The outline is undulating due to localized differences in meristematic activity.
Anthoceros (Hornwort) Thalli. These are relatively small, flat organisms that can form mats. They live in wet environments. It is difficult to see the individual plants which make up this mat.
Thalli of Anthoceros: The red lines indicate the margins of the individual Thalli.
Unusual Thalli of Anthoceros grown in culture. The Margins are deeply indented.
The Chloroplasts from Anthoceros resemble those found in certain Green Algae. Each cell has only one Chloroplast. They contain a Pyrenoid which occurs in the Chlorophyta but is not found in any other terrestrial plant.
These Thalli of Pallavicinia are translucent. and are once cell thick along the margins. They have a ribbon-like shape due to the activity of an Apical Meristem (Apical Cell) at the tip of each Thallus. They also have a thick "Midrib" that contains conducting cells.	The lower surface has hair-like Rhizoids.
This is an SEM image of the under (Ventral) side of a thallose liverwort: Note the location of the Apical meristem and the Rhizoids.