Most moss species are just a few inches tall, are often soft, hairy or fuzzy; they are an appealing shade of deep, saturated green. Although they superficially resemble small plants, mosses lack a vascular system for water or nutrient distribution, and they reproduce in unique ways. Botanically, mosses are classified as bryophytes, and are closely related to liverworts and hornworts. Mosses grow on soil, rocks and trees, often in moist habitats; some even grow underwater. Different species of mosses can be found all over the world, from the Arctic Circle to tropical jungles.
Mosses lack true roots, but they do have grasping, rootlike structures called rhizoids. The aboveground parts can be delineated into two sections: the gametophyte and the sporophyte. The gametophyte is the base of the moss, with a stem and a soft cluster of leaves. Above the gametophyte is the sporophyte, which consists of a stem (or seta), a spore capsule and the calyptra, a membranous hood that protects the capsule. Although the gametophyte and the sporophyte appear to be one discrete structure, they are actually two separate plants growing intertwined.
Mosses do not produce flowers or seeds and instead reproduce with spores, like fungi or ferns. When a spore is released from an adult moss, it must find a moist place in which to germinate. At germination, the spore produces tiny green filaments called protonema, which in turn produce buds that eventually mature into the stem and leaves of the gametophyte. In some moss species, male parts (antheridium) and female parts (archegonium) are produced on separate gametophytes, while in other species they appear together on the same plant. In any case, sperm cells from the male parts are transferred, often by rainwater, to the egg in the female parts, and a zygote is formed. This zygote divides many times and grows into the sporophyte, which lodges itself on top of the gametophyte. The sporophyte grows into a stalk with a capsule on top and the calyptra on top of that. The capsule consists of the base (urn) and a lid (operculum), and inside are the peristome, which resemble two rows of tiny teeth. The peristome help keep the spores inside until they are mature and ready to be distributed.
Indentifying Moss Species
Worldwide there are hundreds of species of moss. Since most are so small, using a hand lens, loupe or magnifying glass will help you identify varieties. Pay attention to the size, shape and position of the capsule, the length of the stalk and the structure of the leaves. Also take note of the surrounding habitat and what kind of substrate the moss is growing on. A good field guide will help you identify mosses that are common to your region.