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Ferns and related (seedless, vascular) plants (Pteridophyta):


Ferns (Filicopsida: all fern families), horsetails (Equisetaceae) and club mosses (Lycopodiaceae) are vascular *, non-flowering plants that do not produce seed (Maddison and Schulz 2004). All of these seedless, vascular plants have a life cycle separated into two distinct stages. The large plant, called the sporophyte (spore producing plant), produces spores by meiosis, the cell division process that creates sex cells. Cells produced by meiosis have only one copy of each gene (i.e. one set of chromosomes rather than two). These “haploid” spores germinate and produce the second life cycle stage called the gametophyte (gamete-producing). Gametophytes are either very small, green, moss-like plants, in the case of most ferns and horsetails, or underground tuber-like plants closely associated with, and dependent upon, specific types of mycorrhizal fungi, in the case of many club mosses. The gametophyte produces haploid sex cells (gametes: sperm and eggs) by ordinary cell division (mitosis). Sperm requires water to swim to the eggs (usually rain). The resulting fertilization produces a diploid sporophyte plant with the standard, two sets of chromosomes (i.e. two copies of each gene). As is evident from the above, these plants produce neither flowers nor seeds. Spores are generally produced in specialized parts of the plant. Ferns may have spore cases (sporangia) on the undersides of some leaves or leaves that specialize entirely in spore case production. Club mosses and horsetails often produce spore cases in cone-like structures, usually at the tips of stems.

*A vascular plant is one with “veins” made up of tube-like xylem and phloem cells that conduct water and nutrients to and from roots and throughout the plant.

Equisetum arvense field horsetail Equisetaceae EQAR; Bx, br, pb, rd, vc, wv; NY; Q, cu, i, j, ri, tl, wl; K, fl; R, c, ca, cp, cs, e, fk, gb, gr, jl, js, jw, k, lp, pm, ro, t, w, wp, wt;

Equisetum arvense Perennial herb, extensively colonial from slender, dark, branching, tuber-bearing underground stems (rhizomes) that can be up to 1.5 m deep and up to 100 m long; new stems can arise from rhizome fragments or tubers; sterile stems to 50 cm tall, green, hollow, thin, rough, jointed, with whorls of leafless, green, horizontal branches from below each node, stems and branches appearing jointed. Leaves: reduced to toothed sheaths around each node, teeth narrow, tips pointed. Spore cones (strobili): brownish, 0.5-3.5 cm tall, on whitish to brown unbranched, fertile stems to 30 cm tall, ephemeral, withering once spores are dispersed (often before sterile stems emerge), ringed by dark, toothed sheaths; appearing early in spring, March-June. Spores produce either male or female gametophytes, green, haploid, moss-like, flat plants 0.2-0.5 cm across that produce eggs and sperm. These unite to form the diploid embryo of the large sporophyte. (Raven et al 1986).Wetland status: FAC. Frequency in NYC: Frequent. Origin: Native. Habitat: Moist to wet open areas, poorly drained soil and high water tables, roadsides, ditches, disturbed sterile soil, fill, railroad embankments; colonies in apparently dry sites usually have rhizomes reaching down to saturated soil. Notes: Forms dense colonies that are important for prevention of soil erosion. Prefers soil pH 4-7, moderately tolerant of shade and anaerobic soil, drought, and salt (USDA, NRCS 2006). Plants eaten by Geese and Muskrats (Martin et al. 1951). Plants contain thiaminase which destroys thiamin, can be toxic. Cell walls contain silica deposits typical for all Equisetum species, which may constitute up to 6.9% dry weight. Field horsetail also tends to accumulate heavy metals (Kingsbury 1964; Cody and Wagner 1981). Tolerant of burning and cutting, stems resprout from rhizomes throughout the growing season. Eaten by Dolerus spp. (Hymenoptera), and possibly by Grypidius equiseti (Coleoptera). Attacked by several fungi including Phoma equiseti (Cody and Wagner 1981). Has been used medicinally as a diuretic (Rook 2004).

Illustration: Equisetum arvense




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