Lycopodiophyta

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Lycopodiophyta

(lī'kōpō'dēŏf`ətə), division of the plant kingdom consisting of the organisms commonly called club mossesclub moss,
name generally used for the living species of the class Lycopodiopsida, a primitive subdivision of vascular plants. The Lycopodiopsida were a dominant plant group in the Carboniferous period, when they attained the size of trees, and contributed to the coal deposits
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 and quillworts. As in other vascular plants, the sporophyte, or spore-producing phase, is the conspicuous generation, and the gametophytegametophyte
, phase of plant life cycles in which the gametes, i.e., egg and sperm, are produced. The gametophyte is haploid, that is, each cell contains a single complete set of chromosomes, and arises from the germination of a haploid spore.
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, or gamete-producing phase, is minute. The living representatives are all rather small herbaceous plants, usually with branched stems and small leaves, but their fossil ancestors were trees. Like other vascular plants, the axes of this group have epidermis, cortex, and a central cylinder, or stele, of conducting tissue. The spore cases, or sporangia, are borne at the base of leaves, either scattered along the stem or clustered into a terminal cone or strobilus. At maturity, the sporangia split across the top, releasing great quantities of spores. The spores germinate to produce small, nongreen, fleshy gametophytes, which bear both sperm-producing antheridia and egg-producing archegonia. The motile sperms swim to the egg through a film of water. The fertilized egg, or zygote, gives rise to an embryo and eventually to a mature sporophyte. The order Lycopodiales includes the common genus Lycopodium, the larger of two genera (the other is Phylloglossum) belonging to this order and containing some 100 species. The order Selaginellales contains only one living genus, Selaginella, with perhaps 600 species, although fossil forms resembling Selaginella are known from deposits of the Carboniferous period (see resurrection plantresurrection plant,
name for several plants, usually of arid regions, that may apparently be brought back to life after they are dead. In reality they have hygroscopic qualities which cause them to curl up when dry and to unfold when moist.
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). The order Isoetales (quillworts) contains the small genus Isoetes, which grows in shallow water in lakes, ponds, and marshy places. The plants have a grasslike appearance and are therefore often not readily identified. The order Lepidodendrales contains members known only from fossil specimens dating from the Upper Devonian to Permian times. LepidodendronLepidodendron and Sigillaria
, two principal genera of an extinct group of primitive vascular trees. They dominated the forests of the early Carboniferous period until the ferns gained ascendancy.
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, the most common genus, was of tree size.

Lycopodiophyta

 

a division of higher sporophytic plants. The leaves, or more precisely the leaf-shaped organs, are called phylloids. They grow in the form of protuberances, or enations, on the stalk. The phylloids are generally simple, with nonbranch-ing veins. Conducting bundles do not form lacunae (leaf gaps). The sporangia are arranged singly in the axils of the leaves or on the stalk above an axil; less commonly, they appear on the upper-part of the leaves. The gametophytes are bisexual or unisexual and form below or above the ground. The Lycopodiophyta, a very ancient group, originated in the Silurian. It flourished in the Carboniferous, at which time it was represented by lepidodendrons and sigillarids. After the Triassic period, the group gradually disappeared. Modern members of the division Lycopodiophyta are classified in the orders Lycopodiales, Sellagin-elaceae, and Isoëtales.

REFERENCES

Takhtadzhian, A. L. Vysshie rasteniia, vol. 1. Moscow-Leningrad, 1956.
Osnovy paleontologii: Vodorosli, mokhoobraznye, psilofitovye, plaunovidnye, chlenistostebel’nye, paporotniki. Moscow, 1963.

Lycopodiophyta

[‚lī·kə·pō·dī′äf·əd·ə]
(botany)
A division of the subkingdom Embryobionta characterized by a dominant independent sporophyte, dichotomously branching roots and stems, a single vascular bundle, and small, simple, spirally arranged leaves.