antheridium (an′ thur id′ ee um) [Gk. antheros: blooming] The multicellular structure that produces the sperm in nonvascular land plants and ferns.antheridium (an′ thur id′ ee um) [Gk. antheros: blooming] The multicellular structure that produces the sperm in nonvascular land plants and ferns.
archegonium (ar′ ke go′ nee um) The multicellular structure that produces eggs in nonvascular land plants, ferns, and gymnosperms.
charales Multicellular green algae with branching, apical growth and plasmodesmata between adjacent cells. The closest living relatives of the land plants they retain the egg in the parent organism.
coleochaetales Multicellular green algae characterized by flattened growth form composed of thin-walled cells. Thought to be the sister-group to the Charales plus land plants.
cuticle (1) In plants, a waxy layer on the outer body surface that retards water loss. (2) In ecdysozoans, an outer body covering that provides protection and support and is periodically molted.
embryophyte See land plants.
euphyllophytes (Euphyllophyta) The group of vascular plants that is sister to the lycophytes and which includes all plants with megaphylls.
gametophyte (ga meet′ oh fyte) In plants and photosynthetic protists with alternation of generations, the multicellular haploid phase that produces the gametes. (Contrast with sporophyte.)
green plants (Viridiplantae) Organisms with chlorophylls a and b, cellulose-containing cell walls, starch as a carbohydrate storage product, and chloroplasts surrounded by two membranes.
heterosporous (het′ er os′ por us) Producing two types of spores, one of which gives rise to a female megaspore and the other to a male microspore. (Contrast with homosporous.)
homosporous Producing a single type of spore that gives rise to a single type of gametophyte, bearing both female and male reproductive organs. (Contrast with heterosporous.)
hornworts (Anthocerophyta) Nonvascular plants with sporophytes that grow from the base. Cells contain a single large, platelike chloroplast.
horsetails (Sphenophyta or Equisetophyta) Vascular plants with reduced megaphylls in whorls.
land plants (Embryophyta) Plants with embryos that develop within protective structures; also called embryophytes. Sporophytes and gametophytes are multicellular. Land plants possess a cuticle. Major groups are the liverworts mosses hornworts and vascular plants.
leptosporangiate ferns (Pteridopsida or Polypodiopsida) Vascular plants usually possessing large, frondlike leaves that unfold from a "fiddlehead," and possessing thin-walled sporangia.
liverworts (Hepatophyta) Nonvascular plants lacking stomata; stalk of sporophyte elongates along its entire length.
lycophytes (Lycopodiophyta) Vascular plants characterized by microphylls; includes club mosses, spike mosses, and quillworts.
megaphyll The generally large leaf of a fern, horsetail, or seed plant, with several to many veins. (Contrast with microphyll.)
megaspore [Gk. megas: large + spora: to sow] In plants, a haploid spore that produces a female gametophyte.
microphyll A small leaf with a single vein, found in club mosses and their relatives. (Contrast with megaphyll.)
microspore [Gk. mikros: small + spora: to sow] In plants, a haploid spore that produces a male gametophyte.
monilophytes (Monilophyta) A group of vascular plants sister to the seed plants characterized by overtopping and possession of megaphylls; includes the ferns horsetails and whisk ferns.
mosses (Bryophyta) Nonvascular plants with true stomata and erect, "leafy" gametophytes; sporophytes elongate by apical cell division.
overtopping Plant growth pattern in which one branch differentiates from and grows beyond the others.
phloem (flo′ um) [Gk. phloos: bark] In vascular plants, the vascular tissue that transports sugars and other solutes from sources to sinks.
rhizoids (rye′ zoids) [Gk. root] Hairlike extensions of cells in mosses, liverworts, and a few vascular plants that serve the same function as roots and root hairs in vascular plants. The term is also applied to branched, rootlike extensions of some fungi and algae.
rhizome (rye′ zome) An underground stem (as opposed to a root) that runs horizontally beneath the ground.
rhyniophytes (Rhyniophyta) A group of early vascular plants that appeared in the Silurian and became extinct in the Devonian. Possessed dichotomously branching stems with terminal sporangia but no true leaves or roots.
seed A fertilized, ripened ovule of a gymnosperm or angiosperm. Consists of the embryo, nutritive tissue, and a seed coat.
sporangium (spor an′ gee um) (plural: sporangia) [Gk. spora: seed + angeion: vessel or reservoir] In plants and fungi, any specialized stucture within which one or more spores are formed.
sporophyte (spor′ o fyte) [Gk. spora: seed + phyton: plant] In plants and protists with alternation of generations, the diploid phase that produces the spores. (Contrast with gametophyte.)
stoma (plural: stomata) [Gk. stoma: mouth, opening] Small opening in the plant epidermis that permits gas exchange; bounded by a pair of guard cells whose osmotic status regulates the size of the opening.
tracheid (tray′ kee id) A type of tracheary element found in the xylem of nearly all vascular plants, characterized by tapering ends and walls that are pitted but not perforated. (Contrast with vessel element.)
tracheophytes See vascular plants.
vascular plant (Tracheophyta) Plants with xylem and phloem. Major groups include the lycophytes and euphyllophytes.
vascular system The conductive system of the plant, consisting primarily of xylem and phloem.
whisk ferns (Psilotophyta) Vascular plants lacking leaves and roots.
xylem (zy′ lum) [Gk. xylon: wood] In vascular plants, the tissue that conducts water and minerals; xylem consists, in various plants, of tracheids, vessel elements, fibers, and other highly specialized cells.