Mosses belong to a group of green plants known as the bryophytes, these are spore-bearing (rather than seed-bearing) plants with poorly developed water and food conducting systems. Mosses solve their water problem by growing where water is always abundant, some mosses are physiologically adapted to survive drought by drying up and going dormant and reviving when the moisture returns. (Most lichens also share this ability, along with some ferns). Structures of the Moss
Mosses are generally very small plants that are composed of a stem that may be branched or unbranched, with leaves arranged around it. This part of the moss is referred to as the gametophyte. The tiny leaves contain a central vein known as a costa which is best viewed under a magnifying glass. When present the sporophyte or spore-bearing structure is usually attached to the top of the leafy stem, or sometimes out from the side of the moss. The sporophyte consists of a capsule on a seta (stalk). The seta is almost never branched and is often shortened in species living in dry conditions. Many mosses also contain a peristome, a cap that covers the top of a gametophyte. Peristomes may consist of 64 "teeth" or 16 lanceolate teeth in either 1 or two rows (this requires magnification to view). Reproduction & Life Cycle
All mosses have a leafy gametophyte body that produces male and female sex organs when mature. Upon fertilization an erect sporophyte develops that is permanently attached to the gametophyte. Within the sporophyte is a spore-producing capsule. Single-celled spores germinate if they happen to land in a suitable growing environment. Upon germination a mat of algae-like filaments is developed. Some of these filaments penetrate the substrate and develop into small root-like appendages called rhizoids. In time small knots of cells appear that enlarge and produce leaves that are arranged around a short stem, from which the gametophyte then grows and develops. Classification of Mosses
True mosses have a sporophyte attached to the gametophyte by a stalk (or seta), they have a cap or operculum on their capsule and they have a peristome, a fringe of "teeth" around their capsule. Mosses are those bryophytes whose capsule maturity takes place after seta elongation.
Sphagnum Mosses are characterized by the lack of a seta and with capsules elevated on the gametophytic stalk instead, the presence of a capitulum (the unique leaf structure with a flattened top), and the lack of a peristome and capsule opening by an operculum.
Liverworts are also bryophytes because like mosses they do not produce seeds, do not have true roots, nor do they have a well developed waterconducting system. They are differentiated from mosses based on complex physiological differences, more obvious differences would be that liverworts may be either leafy or thalloid (having a thallus instead of leaves) while mosses are always leafy.
Clubmosses are not bryophytes at all but are similar in appearance and thus are often confused with mosses and as such are included here for comparisons. Clubmosses are spore bearing plants like mosses but they differ physiologically and are more closely related to Horsetails, and are often grouped together with ferns.
True Mosses: Small Mosses: Pipecleaner Moss (Rhytidiopsis robusta), Tree Moss (Climacium dendroides), Menzie's Tree Moss (Leucolepis acanthoneuron), Juniper Moss (Polytrichium juniperinum), Awned Haircap Moss (Polytrichium piliferum), Fan Moss (Rhizomnium glabrescens), Crane's Bill Moss (Atrichum selwynii), Wavy Leaved Cotton Moss (Plagiothecium undulatum), Bent Leaf Moss (Rhytidiadelphus squarrosa), Goosenecked Moss (Rhytidiadelphus triquetrus), Broom Moss (Dicranum scoparium), Curly Hypnum (Hypnum subimonens), Swamp Moss (Philonotis fontana), Small Flat Moss Pseudotaxiphylum elegans
True Mosses: Large and Feather Mosses: Hairy Step Moss (Hylocomium splendens), Big Red Stem (Pleurozium schreberi), Oregon Beeked Moss (Kindbergia oregana), Douglas Neckera (Neckera douglasii), Menzie's Neckera (Metaneckera menziesii), Cat Tail Moss (Isothecium myosuroides), Badge Moss (Plagiomnium insigne), Black Tufted Rock Moss (Racomitrium aciculare)
Sphagnum Mosses: Green Sphagnum (Sphagnum girgensohnii), Small Red Sphagnum (Sphagnum capillifolium), Fat Bog Moss (Sphagnum papillosum), Brown-Stemmed Bog Moss (Sphagnum lindbergii)
Liverworts: Ring Pellia (Pellia neesiana), Tree Ruffle Liverwort (Porella navicularis), Snake Liverwort (Conocephalum conicum), Cedar Shake Liverwort (Plagiochila porelloides), Common Fold Leaf Liverwort Diplophyllum albicans, Hanging Millipede Liverwort Frullinaria nisquallensis
Clubmosses: Running Clubmoss (Lycopodium clavatum), Mountain Clubmoss (Lycopodium selago), Stiff Clubmoss (Lycopodium annotinum), Ground Cedar (Lycopodium complanatum), Wallace's Selaginella (Selaginella wallacei)
