The spores were oval and the spore wall was smooth.

Study of the spore wall indicates a relationship with the liverworts.

However, this requires that the spore walls be sturdy and resistant at an early stage.

The spore walls are thin, up to 0.2 μm.

In some genera, the spore walls are drawn out into long processes which are thought to slow sinking through the water column.

Gametophytes, as with all heterosporous plants, develop within the spore wall.

These two cells in addition to the spore wall make up an immature pollen grain.

These appendages develop from an outer spiral layer of the spore wall.

The spore wall is brown, smooth, about 0.8-1 μm thick, and has a germ pore.

The spore wall may be thin to thick (up to 0.5 m).