Liverworts and Mosses (Bryophytes)
The Liverworts and Mosses, bryophytes, are relatively small plants with numerous round chloroplasts in each cell.
Mosses are simple in structure, tiny and leafy arrangements found around the thallus exhibiting radial or spiral symmetry.
Liverworts, on the other hand, have foliose and thallus which are green-leaf like arrangements attached to the stem.
Mosses and liverworts are tiny plants that produce spores instead of flowers and seeds.
Mosses and liverworts do differ, but they share enough important characteristics to be known collectively as bryophytes.
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 which are small, flattened green plants.
Some of these lack distinct development of stems and leaves while others possess these types of structures.
The true mosses with distinct stems and leaves are probably the best known of the mosses. They can be widespread and under proper conditions forming extensive bogs.
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 communities of small plants and animals usually inhabit masses of these mosses.
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