Liverworts and Mosses (Bryophytes)
The bryophytes are relatively small plants with numerous round chloroplasts in each cell. They are lacking the flowers and specialized water conducting cells of vascular plants. However, water may be retained in tissues of these plants for considerable periods of time due to the presence of numerous empty cells scattered throughout the plant body.
The life cycle of bryophytes typically consists of two phases; first, the leafy green gametophyte that produces motile gametes and second the usually brownish non-leafy sporophyte generation that produces spores.
About 45 genera of these plants occur in or near fresh waters of North America. Of these, about 12 are liverworts (class Hepaticae) which are small, flattened green plants.
Some of these lack distinct development of stems and leaves while others possess these types of structures. Riccia is a slender branched liverwort usually floating individually just beneath the surface of ponds, canals and ditches. Often common in the same environment, Ricciocarpus is a notched, semicircular form about 1 cm in diameter with black rhyzoids on the under surface. Jungermannia is a leafy liverwort found in streams and slow waters.
The true mosses, those bryophytes with distinct stems and leaves, are in the class Muscixteat moss éphagnum is probably the best known of the mosses. It is widespread and under proper conditions forms extensive bogs. Fontinalis and a number of other true mosses often occur in large waving masses, particularly in spring and mountain streams.
These are typically long, sinuous plants with thick set leaves arising in various fashions along the stem. Interesting assemblages of small plants and animals usually inhabit masses of these mosses.