Most people think mosses, liverworts, hornworts, and lichens are similar, but these organisms are in very different groups. Mosses, liverworts, and hornworts are small, low plants usually found in damp habitats. They lack veinlike structures and do not produce flowers or seeds — instead, they produce spores. Meanwhile, lichens are not plants at all: they are a collection of different fungi that have photosynthetic algae living within their tissues.
Lichens: Fungi With Algae Under Their Skin
Missouri has about 436 species of lichens. Because they are composite organisms formed by a fungus species and an alga, lichens are not plants. Still, many lichens are green because of photosynthetic algae that live just under their top surfaces. Lichens have an amazing variety of growth forms that can be boiled down to “crusty,” “leafy,” or “shrubby.” Unlike most bryophytes, lichens can usually survive in dry, sunny locations.
Importance
Mosses, liverworts, hornworts, and lichens are fascinating organisms that add beauty and mystery to the landscape. They are important for holding soils against erosion and play a critical role in the early stages of ecological succession, as plants begin to colonize a disturbed or barren landscape. Their absence can be an important indicator of pollution. Some species are important for human industry. Many birds and other animals use them in nest building. Many tiny animals need them as habitat. They’re all around us. They are fun to look at and identify — all you need to get started is a hand lens or a camera that takes good closeups.
For a long time, mosses, liverworts, and the small group of plants called hornworts were placed together in a single division of the plant kingdom: division Bryophyta. Today, each has its own division, and only mosses remain in the true Bryophyte group. But many people still refer to these three groups of plants collectively as bryophytes, with a little “b,” because they have much in common:
- small size, low stature
- usually prefer moist habitats
- lack a vascular (veinlike) system for transporting fluids and nutrients
- do not produce flowers or seeds
- produce spores
- have a two-part life cycle with alternating generations of gametophytes (egg- and sperm-producing plants) and sporophytes (spore-producing plants).
Missouri has approximately 315 species of mosses, 112 species of liverworts, and 4 species of hornworts.