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adventitious roots -- A root that grows from somewhere other than the primary root, for example, roots that arise from stems or leaves.
alternation of generations -- Life cycle in which haploid and diploid generations alternate with each other.
anemophily -- Seed plants which are pollinated by wind are said to be anemophilous.
angiosperm -- n. A group of plants that produce seeds enclosed within an ovary, which may mature into a fruit; flowering plants.
anther -- The pollen producing tip of a stamen; part of a flower. More info?
antheridium -- The organ on a gametophyte plant which produces the sperm cells.
anthophyte -- A flowering plant, or any of its closest relatives, such as the Bennettitales, Gnetales, or Pentoxylales.
apical meristem -- Group of cells at the growing tip of a branch or root. It divides cells to create new tissues.
archegonium -- The organ on a gametophyte plant which produces the egg cell, and nurtures the young sporophyte.
axil -- The angle formed between a leaf stalk and the stem to which it is attached. In flowering plants, buds develop in the axils of leaves.
bipinnate -- Describing a pinnate leaf in which the leaflets themselves are further subdivided
in a pinnate fashion.
bisporangiate -- When a flower or cone produces both megaspores and microspores, it is said to be bisporangiate. Most flowers are bisporangiate.
blade -- Any broad and flattened region of a plant or alga, which allows for increased photosynthetic surface area.
bract -- Any reduced leaf-like structure associated with a cone or flower.
bryophyte -- Plants in which the gametophyte generation is the larger, persistent phase; they generally lack conducting tissues. Bryophytes include the Hepaticophyta (liverworts), Anthocerotophyta (hornworts), and Bryophyta (mosses).
carpel -- A unit of the pistil; it is evolutionarily a modified leaf.
cataphyll -- In cycads, a scale-like modified leaf which protects the developing true leaves.
columella -- A small column of tissue which runs up through the center of a spore capsule. It is present in hornworts, mosses, and some rhyniophytes.
compound leaves -- n. Leaves with two or more leaflets attached to a single leaf stem.
cotyledon -- n. The "seed leaves" produced by the embryo of a seed plant that serve to absorb nutrients packaged in the seed, until the seedling is able to produce its first true leaves and begin photosynthesis; the number of cotyledons is a key feature for the identification of the two major groups of flowering plants.
elater -- A cell or part of a cell which assists in dispersing spores. The elaters change shape as they lose or acquire water, and they will then push against surrounding spores.
embryophyte -- Synonym for the Plantae, as here defined. It includes all green photosynthetic organisms which begin the development of the sporophyte generation within the archegonium.
enations -- Flaps of tissue such as those found on psilophytes.
endodermis -- Literally "inner skin", this is a layer of cells which surrounds the central core of vascular tissue, and which helps to regulate the flow of water and dissolved substances.
entomophily -- Seed plants which are pollinated by insects are said to be entomophilous.
epiphyte -- A plant which grows upon another plant. The epiphyte does not "eat" the plant on which it grows, but merely uses the plant for structural support, or as a way to get off the ground and into the canopy environment.
eustele -- When a plant's vascular tissue develops in discrete bundles, it is said to have a eustele. See also protostele and siphonostele.
fiber -- Elongated and thickened cell found in xylem tissue. It strengthens and supports the surrounding cells.
flower -- Collection of reproductive structures found in flowering plants. More info?
fruit -- In flowering plants, the structure which encloses the seeds. True fruits develop from the ovary wall, such as bananas and tomatoes, though not all fruits are edible, such as the dry pods of milkweed or the winged fruits of the maple.
grain -- (1) The texture of wood, produced by the kinds of xylem cells present. (2) The fruit of a member of the grasses.
guard cells -- Pair of cells which surround a stomate and regulate its size by altering their shape.
gymnosperm -- n. A plant that produces seeds, which are not enclosed; includes any seed plant that does not produce flowers.
gynostemium -- The central reproductive stalk of an orchid, which consists of a stamen and pistil fused together.
habit -- The general growth pattern of a plant. A plant's habit may be described as creeping, trees, shrubs, vines, etc.
herb -- Generally any plant which does not produce wood, and is therefore not as large as a tree or shrub, is considered to be an herb.
heterosporangiate -- Producing two different kinds of sporangia, specifically microsporangia and megasporangia. Compare with heterosporous.
heterosporous -- Producing two different sizes or kinds of spores. These may come from the same or different sporangia, and may produce similar or different gametophytes. Contrast with homosporous, and compare with heterosporangiate.
holdfast -- Anchoring base of an alga.
homosporous -- Producing only one size or kind of spore. Contrast with heterosporous.
hypha -- n.Threadlike filaments that form the mycelium (body) of a fungus; hyphae- pl.
inflorescence -- A cluster of flowers.
internode -- The region of a stem between two nodes, when there is no branching of the vascular tissue.
lamina -- Any broad and flattened region of a plant or alga, which allows for increased photosynthetic surface area.
leaf -- An organ found in most vascular plants; it consists of a flat lamina (blade) and a petiole (stalk). Many flowering plants have additionally a pair of small stipules near the base of the petiole.
leaf trace -- The strand of vascular tissue which connects the leaf veins to the central vascular system of the stem.
leaflet -- In a compound leaf, the individual blades are called leaflets.
magnoliid -- Any member of the basal assemblage of flowering plants.
mannoxylic -- Wood in which there is a great deal of parenchyma tissue among the xylem is called mannoxylic. Cycads and pteridosperms have mannoxylic wood. Contrast with pycnoxylic.
megaspore -- In plants which are heterosporous, the larger kind of spore is called a megaspore; it usually germinates into a female (egg-producing) gametophyte. Contrast with microspore.
meristem -- Group of undifferentiated cells from which new tissues are produced. Most plants have apical meristems which give rise to the primary tissues of plants, and some have secondary meristems which add wood or bark.
merophytes -- Group of cells which have all been produced from the same initial cell. Leaves and stems in particular are often built from specific patterns of merophytes.
microphyll -- A kind of leaf, specifically one which has a single, unbranched vein in it. Microphylls are only found in the lycophytes.
microspore -- In plants which are heterosporous, the smaller kind of spore is called a microspore; it usually germinates into a male (sperm-producing) gametophyte. Contrast with megaspore.
mycorrhizae -- Symbiotic association between a fungus and the roots or rhizoids of a plant. More info?
node -- The region of a stem between two internodes, where there is branching of the vascular tissue into leaves or other appendages.
ovary -- In flowering plants, the part of the flower which encloses the ovules. When the ovary matures, it becomes the fruit.
ovule -- In seed plants, the structure which gives rise to the seed.
paleoherb -- Any member of a group of basal flowering herbs which may be the closest relatives of the monocots. They include the water lilies, Piperales, and Aristolochiales.
parenchyma -- A generalized cell or tissue in a plant. These cells may manufacture or store food, and can often divide or differentiate into other kinds of cells.
perennial -- A plant which continues to grow after it has reproduced, usually meaning that it lives for several years.
perianth -- The sepals and petals of a flower are together called the perianth; literally "around the anthers". More info?
peristome -- A set of cells or cell parts which surround the opening of a moss sporangium. In many mosses, they are sensitive to humidity, and will alter their shape to aid in spore dispersal.
petal -- One of the outer appendages of a flower, located between the outer sepals and the stamens. Petals often display bright colors that serve to attract pollinators. More info?
phloem -- Nutrient-conducting tissue of vascular plants.
phragmoplast -- The cell plate formed during cell division.
phytomelanin -- a papery "sooty" black layer over the seed of plants in the Asparagales, which includes agaves, aloes, onions and hyacinths. It is an important character for defining the group.
pinnately compound -- Leaves which are divided up like a feather are said to be pinnately compound.
pistil -- The central set of organs in a flower; it is composed of one or more carpels. More info?
pith -- To severely damage the brain of a frog, also any central region of parenchyma tissue within a plant stem.
pits -- Thin regions of the cell wall in xylem conducting cells. Their structure is an important characteristic for recognizing different kinds of wood.
plasmodesmata -- Cytoplasmic connections between neighboring cells in plant tissues.
platyspermic -- Having seeds which are flattened and disc-like. Contrast with radiospermic.
plicate -- Folded like a paper fan, as in the leaves of palms, cyclanthoids, and some orchids.
pollen -- The microspore of seed plants.
pollen tube -- In seed plants, the extension of the male gametophyte as it emerges from the pollen grain in search of the female gametophyte.
pollination -- Process of transferring the pollen from its place of production to the place where the egg cell is produced. This may be accomplished by the use of wind, water, insects, birds, bats, or other means. Pollination is usually followed by fertilization, in which sperm are released from the pollen grain to unite with the egg cell.
pollinia -- A mass of fused pollen produced by many orchids.
protostele -- When a plant's vascular tissue develops in a solid central bundle, it is said to have a protostele. See also siphonostele and eustele.
pseudoelaters -- Moisture-sensitive cells produced in the sporangium of hornworts.
pteridophyte -- Plant in which the sporophyte generation is the larger phase and in which the gametophyte lives an existence independent of its parent sporophyte. Pteridophytes are almost all vascular plants, and include the lycophytes, trimerophytes, sphenophytes, and ferns.
pteridosperm -- An extinct group of seed plants which bore fern-like leaves.
pycnoxylic -- Wood in which there is little or no parenchyma tissue among the xylem is called pycnoxylic. Conifers and flowering plants have pycnoxylic wood. Contrast with mannoxylic.
radicle -- The end of a plant embryo which gives rise to the first root.
radiospermic -- Having seeds which are round or ovoid. Contrast with platyspermic.
reticulate -- Interconnecting, like a network.
rhizoid -- n. A cellular outgrowth of a plant that usually aids in anchoring to the surface and increasing surface area to acquire water or nutrients; found in mosses, liverworts, and hornworts.
rhizome -- n. A horizontal underground stem, such as found in many ferns, where only the leaves may stick up into the air; sphenophytes (horsetails and their relatives) spread via rhizomes, but also produce erect stems.
root -- Usually the below ground portion of a plant. Contrast with shoot.
rosette -- A series of whorls of leaves or leaf-like structure produced at the base of the stem, just above the ground.
secondary growth -- Growth in a plant which does not occur at the tips of the stems or roots. Secondary growth produces wood and bark in seed plants.
sepal -- The outermost structures of a flower. More info?
shoot -- Usually, the above ground portion of a plant, bearing the leaves. Contrast with root.
siphonostele -- When a plant's vascular tissue develops as a central cylinder, it is said to have a siphonostele. See also protostele and eustele.
spermatophyte -- A seed plant.
sporangiophore -- A stalk to which sporangia are attached.
sporangium -- A chamber inside of which spores are produced through meiosis.
sporophyll -- Any leaf which bears sporangia is called a sporophyll.
stamen -- Part of a flower, the tip of which produces pollen and is called the anther. More info?
stigma -- The sticky tip of a pistil. Or, the dense region of pigments found in many photosynthetic
protists which is sensitive to light, and thus functions somewhat like a miniature eye.More info?
stipe -- A scientific term for "stalk".
stipules -- Paired appendages found at the base of the leaves of many flowering plants.
stomata -- Openings in the epidermis of a stem or leaf of a plant which permit gas exchange with the air. In general, all plants except liverworts have stomata in their sporophyte stage.
streptophytes -- The clade consisting of the plants plus their closest relatives, the charophytes.
strobilus -- A tightly clustered group of sporophylls arranged on a central stalk; commonly termed a "cone" or "flower".
style -- The narrow stalk of the pistil, located above the ovary but below the stigma.
synangium -- A cluster of sporangia which have become fused in development.
tepal -- When the sepals and petals of a flower are indistinguishable, they are referred to as tepals. Tepals are common in many groups of monocots. More info?
thalloid -- Plants which have no roots, stems, or leaves are called thalloid, such as liverworts and hornworts.
tracheophyte -- Any member of the clade of plants possessing vascular tissue; a vascular plant.
tree -- Any tall plant, including many conifers and flowering plants, as well as extinct lycophytes and sphenophytes.
tuber -- An underground stem which has been modified for storage of nutrients, such as a potato.
turgor pressure -- Force exerted outward on a cell wall by the water contained in the cell. This force gives the plant rigidity, and may help to keep it erect. More info?
vegetative growth -- Growth of a plant by division of cells, without sexual reproduction.
venation -- The arrangement and pattern of veins in a leaf.
whorl -- An arrangement of appendages, such as branches or leaves, such that all are equally spaced around the stem at the same point, much like the spokes of a wheel or the ribs of an umbrella
wood -- A secondary tissue found in seed plants which consists largely of xylem tissue.
xylem -- Water-conducting tissue of vascular plants.