Bryophyta
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Read about Bryophyta in the Standard Cyclopedia of Horticulture
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Bryophyta (Mosses and Liverworts) Small green plants of simple structure, either thalloid or differentiated into stem and leaves: true roots wanting: vascular tissue absent: alternation of generations well developed, the gamete-bearing generation dominant: female gamete (egg) inclosed in a flask-shaped multicellular archegonium : male gametes (sperm-cells) inclosed within a multicellular antheridial wall: fertilized egg producing the spore-bearing generation (sporogonium) which consists of a parasitic or semi-parasitic capsule usually borne upon a seta. The Bryophytes are divided into two great classes, namely the Hepaticae (Liverworts) and the Musci (Mosses). Each of these in turn is divided into several orders, which, as usual, contain one or more families. Mosses and liverworts are widely distributed over the earth, the latter seeming to prefer limestone regions. The Hepaticae are characterized by a spore-bearing generation consisting of a stalked or sessile simple capsule, which contains spores and elongated sterile elaters, and splits into teeth or valves at maturity. The plant body (gamete-bearing generation) consists either of a thalloid, algal-like, dichotomously branching, ribbon-like structure, or of a slender axis bearing the very thin leaves, one cell in thickness, and destitute of a midrib. The leaves are usually arranged in two lateral rows, with often a third row of small dissimilar leaves on the under side, so that the shoot is strongly dorsi-ventral. The lateral leaves frequently bear at the base a curious lobe that is infolded or even flask-shaped, and probably aids in the conservation of water on the dry rocks and tree trunks which many of these plants frequent. The under side of the stem or thallus is usually provided with rhizoids that take the place of roots. The thalloid liverworts are inhabitants of damp or wet situations, some being aquatic: in the North, they are found on damp soil, wet rocks, or among damp moss. The majority of foliose liverworts inhabit similar places, only comparatively few genera and species being xerophytic. Filaments of the alga, Nostoc, penetrate the cavities in the thallus of Anthoceros and there form endophytic colonies. Vegetative reproduction is accomplished by the branching of the thallus, or by the production of special buds, called gemmae, either on the edge of the leaf or thallus, or in special cup-like receptacles borne on the surface of the thallus. The Hepaticae are divided into four principal orders as follows: Order I.—Ricciales. Thalloid, floating or amphibious: sexual organs sunken in the thallus: capsule sessile, thin-walled, endophytic, irregularly dehiscent. Order II.—Marchantiales. Thalloid: archegonia and antheridia usually borne on special branches of the thallus: capsule often stalked, usually regularly dehiscent. Marchantia was formerly used as a remedy in diseases of the liver, hence the name liverwort. Order III.—Anthocerotales. Thalloid: one chloroplast in each cell: sexual organs superficial: capsule very slender, chlorophyll- and stomate-bearing, continuing to elongate by basal growth. Order IV.—Jungermanniales. Thalloid or foliose: capsule usually splitting to the base into four valves. The Musci (Mosses) differ from the Hepaticae mainly in the more elaborate capsule, which in the young state commonly contains chlorophyll, is provided with stomates, and contains a central column of sterile tissue (columella) encircled by the spore-bearing chamber. The dehiscence of the capsule is apical and transverse, and consists in the formation of a lid (operculum) which falls off exposing the mouth of the annular spore-chamber. This mouth is surrounded by a single or double row of numerous hygroscopic teeth (peristome), which, by their bending, regulate the escape of spores in wet and dry weather. No elaters are produced. The sporogonium of the moss is, therefore, not only a more independent structure from the standpoint of nutrition than is that of most liverworts, but is constructed along wholly different lines. On the summit of the capsule is usually found a delicate, diversely shaped, hood-like cap not organically connected with it and easily detached, called the calyptra. This is the enlarged upper portion of the archegonium, which, after rupture, is borne aloft on the summit of the growing sporogonium. The plant-body (gamete-bearing generation) is never thalloid; and the leaves, which are provided with a midrib, are frequently of several cells in thickness. The germination of the spore does not result at once in a moss plant, but produces a creeping filamentous branched, algal-like growth (protonema) on which at length are borne the buds that give rise to the moss-stem proper. The Musci are subdivided as follows: Order I.—Sphagnales (Bog or Peat Mosses). Structure of stem and leaf peculiar, consisting of dead, tracheid-like cells without protoplasm and provided with pits or thickening bands, regularly interspersed among slender, living cells containing protoplasm and chloroplastids. Under ordinary conditions, the tracheid-like cells are filled in part with air, and hence the plant has a grayish hue. In the presence of rain or abundant soil-water, the water is drawn into the cells by capillarity until the still apparently dry plant contains a surprisingly large quantity of water, which will flow out on squeezing in the hand. The capsule possesses no peristome, and the spore-sac is continuous over the top of the columella. Peat mosses are large, branched plants growing in extensive colonies in wet or damp situations in northern countries. They are especially abundant on the floating moors which surround certain small ponds, and by their decay play an important part in the filling in of these ponds. They continue to thrive in these "bogs" until the conditions at length become too dry. Peat mosses, therefore, form a large component of “peat,” and in this way the Sphagnales have played a very interesting part in the evolution of the present surface of the earth. Because of the power to retain water, sphagnum is of economic importance to nurserymen and florists, who use this moss extensively in packing stock for shipment, in germinating seeds, and for other purposes. Some species of sphagnum are eaten in Lapland by the reindeer. Mixed with the hair of the reindeer, they are used for stuffing mattresses. Order II.—Andreales. A small group of rock mosses. The spore-chamber is continuous over the summit of the columella, and the capsule dehisces by four longitudinal slits. Order III.—Phascales. A small group of minute terrestrial mosses with few leaves, but a persistent protonema: capsule indehiscent, at length decaying. Order IV.—Bryales. A large group containing the majority of the mosses: capsule dehiscing by an operculum; peristome present; spore-sac interrupted at the summit by the columella. Certain species were formerly used as astringents and diuretics. Leskea sericea has been used to stop the flow of blood from wounds. Species of Hypnum and Fontenalis are used in Norway and Sweden, by the peasants, to fill cracks in the walls of huts. Hypnum triquetrum is sometimes used in place of sphagnum for packing plants. With the exception of sphagnum, the mosses and liverworts do not seem to be in the trade.
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
External links
- w:Bryophyta. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
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