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adaptive radiation – Rapid evolution of a group of related organisms into unoccupied ecological niches.
adventitious root – A root of a vascular plant that arises anywhere other than from the radicle or the zone of lateral root formation.
akinete – A resistant resting spore of Cyanobacteria, equivalent to an endospore of Eubacteria.
alga ( algae) – A photosynthetic organism that is not a member of the eubacteria or the Kingdom Plantae.
alternation of generations – The alternation of a diploid, meiospore- producing generation, the sporophyte, with a haploid, gamete-producing generation, the gametophyte, in the life history of a plant.
analogy – Non-homologous similarity of structure resulting from similarity of function.
ancestral character – See plesiomorphy.
androecium ( androecia) – The microsporangiate part of the flower; all the stamens collectively.
anisogamous – Having flagellated gametes that differ in size and structure.
anther – Cluster of one or more microsporangia in the Anthophyta, attached to a filament to form a stamen.
antheridiophore – In some liverworts, an elevated structure bearing antheridia.
antheridium ( antheridia) – The male gametangium, consisting of a single specialized cell or group of cells in which sperm are produced.
anthocyanin – One of a class of water-soluble pigments usually found in the vacuoles of plant cells; anthocyanins are often blue, pink, or yellow.
aplanospore – A nonmotile spore.
apomorphy – A homology which has originated as a new evolutionary feature within a group under study.
apothecium ( apothecia) – Cup-shaped, open ascocarp containing asci on its inner exposed surface.
archegoniophore – In some liverworts, an elevated structure bearing archegonia.
archegonium ( archegonia) – A multicellular female gametangium found in the embryophytes.
ascocarp – The meiosporangium-producing structure in Ascomycota including the asci and the ascospores.
ascospore – Meiospore produced in an ascus by the Ascomycota.
ascus ( asci) – The meiosporangium of the Ascomycota.
aseptate – Descriptive of a hypha or filament lacking cross-walls between the nuclei; ordinarily used to describe fungi. See also coenocytic.
asexual phase – The portion of an organisms life cycle devoted to asexual reproduction.
asexual reproduction – Formation of offspring that are genetically identical to the parent, by mitotic division.
autotrophic – The ability to synthesize high-energy carbon compounds from inorganic raw materials using energy from sunlight or from certain inorganic chemical reactions.
auxospore – The zygote of a diatom. Lacking a silica cell wall, an auxospore is able to expand in size.
axenic – A pure culture of an organism, containing no foreign organisms.
axillary bud – A meristem, or bud, located on a stem just above the attachment of a leaf; ordinarily found in seed plants.
basal body – The structure that attaches a flagellum or cilium to a cell.
basidiocarp – The meiosporangium-producing structure of the Basidiomycota.
basidiospore – Meiospore produced in a basidium by the Basidiomycota.
basidium ( basidia) – The meiosporangium of the Basidiomycota.
binary fission – Reproduction of a prokaryote, chloroplast, or mitochondrion by division into two equal parts.
binomial nomenclature – The system for naming organisms developed by Carl Linnaeus, in which every organism has a generic name and a specific epithet.
bisexual – 1. In gametophytes, possessing both antheridia and oogonia or archegonia. 2. In sporophytes, possessing both microsporangia and megasporangia.
blade – The flattened portion of a leaf or leaf-like structure. See petiole.
bract – A modified leaf, often reduced in size and with little photosynthetic capability.
calyptra ( calyptrae) – in mosses, the expanded tip of the archegonium that covers the end of the capsule of the sporophyte.
calyx ( calyces) – All of the sepals collectively; in a complete flower, the outermost whorl of parts.
capsule – A meiosporangium, especially of bryophytes.
carbonization – Process of fossilization in which heat and pressure of the rock layers drive off all volatile elements from remains of organisms, leaving only carbon.
carotenoid – A class of fat-soluble photosynthetic accessory pigments.
carpel – The megasporophyll of the Anthophyta; one or more carpels form a pistil.
carpogonium ( carpogonia) – In the Rhodophyta, the organ of the gametophyte that houses the egg; equivalent to oogonium.
carpospore – A diploid spore in the Rhodophyta which is produced by the carposporophyte and gives rise to the tetrasporophyte.
carposporophyte – The first of two successive diploid generations in the Rhodophyta, developing from the zygote and producing carpospores.
casparian strip – A region of the radial cell walls of the endodermis that is impregnated with suberin and that prevents apoplastic transport.
cellulose – A polysaccharide composed of glucose subunits. Cellulose is a major cell wall constituent in the Kingdom Plantae and several divisions in the Protista.
centriole – The intracellular organelle that represents an inactivated basal body. Centrioles do not occur in the Kingdom Fungi and the divisions Coniferophyta, Gnetophyta, and Anthophyta of the Kingdom Plantae.
centromere – The portion of a chromosome that binds sister chromatids and that attaches to the spindle.
chitin – A polysaccharide composed of amino sugar subunits. Chitin is the primary cell wall constituent in the Kingdom Fungi.
chlorophyll – The green, magnesium-containing pigment found in all photosynthetic organisms.
chloroplast – The intracellular organelle that carries out photosynthesis.
chromatid – One of the two replicated strands of DNA and associated proteins forming a chromosome following replication.
chromosome – One or more united chromatids forming one of several units in a eukaryotic genome.
circinnate vernation – Unfolding of a newly-formed leaf in a spiral structure.
circular reasoning – See tautology.
clade – See monophyletic group.
cladistic classification – Classification of organisms based on evolutionary kinship.
cladogram – A graphic hypothesis of the phylogeny of a group of organisms, based on the distribution of shared homologies in the group.
classification – Arrangement of entities into orderly groups.
cleistothecium ( cleistothecia) – Spherical, closed ascocarp containing asci in its interior.
coal ball – A carbonate rock surrounding carbonized plant (or rarely animal) material, generally found as an inclusion in coal strata.
coenocytic – Consisting of multinucleate filaments or other structures; ordinarily used for algae. See also aseptate.
colony – A group of cells, usually the asexual offspring of a single original cell, that do not show division of labor and that do not form a filament.
columella ( columellae) – a central cylinder or dome of sterile tissue in the center of a sporangium.
complete flower- A flower with sepals, petals, stamens, and pistils.
compression fossil – The organic remains of an organism which have been pressed flat between rock strata.
conceptacle – a chamber at the tip of a branch of a rockweed in the Phaeophyta that contains the oogonia and antheridia.
conidiophore – The hypha that produces conidia.
conidiospore – See conidium.
conidium ( conidia) – An asexual spore of the Ascomycota produced on a conidiophore. Conidia form in linear chains.
coralloid root – A root of plants in some Cycadophyta that is formed at the surface of the soil and that contains symbiotic cyanobacteria that provide nitrogen fixation.
corolla – All of the petals collectively.
cortex ( cortices, cortexes) – in a member of the Kingdom Plantae, the tissue composed of parenchyma cells that lies inside the epidermis and outside the vascular tissue.
cotyledon – A seed leaf present as part of an embryonic seed plant sporophyte. Cotyledons absorb nutrients from the female gametophyte or endosperm, and in some species are also photosynthetic after germination of the seed.
crossing-over – Exchange of parts between two paired chromosomes during meiosis, resulting in new combinations of linked genes within the resulting haploid cells.
crustose – a form of lichen in which the thallus is thin and closely appressed to the substrate.
cuticle – A waxy layer formed on the outer tangential walls of epidermal cells in the Kingdom Plantae.
cyanobacterium ( cyanobacteria) – A photosynthetic prokaryote of the Division Cyanophyta.
cytokinesis ( cytokineses) – Cytoplasmic division in mitosis or meiosis.
deciduous – Detaching and falling away from the main plant body, as a normal occurrence.
dehisce – Split open to release something, usually spores or seeds.
derived character – See apomorphy.
determinate growth – Cessation of ontogeny when an organism reaches its final adult form; characteristic of animals. See indeterminate growth.
diatomaceous earth – a sedimentary rock formed of the silica cell walls of diatoms (division Bacillariophyta).
dichotomous – Branching by division into two more or less equal parts.
dicot – A member of the Division Anthophyta, Class Magnoliopsida. This class is characterized by having two cotyledons, a feature shared with most other seed plants.
dioecious – Seed plant sporophytes producing either seeds or pollen, but not both.
diploid – Having two complete genomes; the chromosome condition resulting from syngamy and necessary for meiosis.
dormancy – Metabolic inactivity of a seed or resistant spore prior to germination.
elater – 1. In liverworts (Hepatophyta) and hornworts (Anthocerophyta), thin filaments made of diploid cells that form among the meiospores and help disperse them. 2. In Equisetum (Sphenophyta), strap-like projections from the meiospore cell walls that coil and straighten with changes in humidity, aiding dipersal.
embryo – sporophyte plant in an early stage of development, usually still within the gametophyte.
embryo sac – The female gametophyte of flowering plants.
embryophyte – A member of the Kingdom Plantae. Having an embryonic sporophyte dependent on the gametophyte for at least the first part of its life.
enation – Projection of tissue from the stem.
endodermis ( endodermes) – A layer of cells surrounding the vascular tissue in roots, stems, or leaves of many seed plants. The endodermis is the innermost layer of the cortex.
endosperm – A nutritive material in seeds of the Anthophyta, formed from the triple fusion nucleus.
endosporic – Of gametophytes, forming inside the meiospore cell wall.
epicotyl – The embryonic shoot of a seed plant.
epidermis ( epidermes) – The outermost cell layer of a plant.
epigynous – Condition of a flower in which the sepals, petals, and stamens seemingly arise from the top of the ovary.
eukaryote – An organism with a membrane-bound nucleus, membrane-bound intracellular organelles, and chromosomes.
eusporangium ( eusporangia) – A meiosporangium that arises from several initial cells and forms a wall of more than one cell layer.
eustele – A stele in which the vascular bundles are arranged in discrete strands around a pith; typical of seed plants.
exosporic – Of gametophytes, forming outside the meiospore cell wall.
fascicle – A group of needle leaves of pine or related conifers that are attached to a single lateral spur shoot.
fertilization – Syngamy.
filament – A structure consisting of many cells joined end-to-end, or a single, large multinucleate cell with the same thread-like appearance.
filamentous – Consisting of filaments.
flagellum ( flagella) – For an individual cell, an organelle of propulsion formed from a cylinder of microtubules attached to a basal body.
flagellated – Having flagella.
floridean starch – the storage polysaccharide of the Division Rhodophyta.
flower – The strobilus of the Anthophyta, in many species containing both megasporangia and microsporangia.
foliose – a form of lichen in which the thallus is thin but elevated above the substrate, and somewhat leaf-like in appearance.
fossil – A remnant or trace of an organism of past geological ages that has been preserved in the Earths crust.
frond – A leaf of a fern.
fruticose – a form of lichen in which the thallus is branched and often cylindric, often resulting in a shrub-like appearance.
fucoxanthin – a xanthophyll pigment characteristic of the Phaeophyta and also found in many Chrysophyta and Pyrrhophyta.
fungus ( fungi) – A heterotrophic, absorptive organism, either of the Kingdom Fungi or of similar ecology.
funiculus ( funiculi) – The stalk that connects the ovule to the ovary wall.
gametangium ( gametangia) – A unicellular or multicellular structure in which gametes are formed.
gamete – A haploid reproductive cell that fuses with another gamete to produce a zygote.
gametophyte – A haploid organism arising from meiospores; produces gametes by mitosis.
gemma ( gemmae) – Multicellular asexual reproductive structures of liverworts, consisting of disc-shaped masses of cells borne in a gemma cup.
generative nucleus – The nucleus of a pollen grain that divides to form the sperm cells.
genome – A complete set of chromosomes inherited as a unit from one parent.
germination – Resumption of active metabolism by a spore or seed, rupture of its outer wall, and beginning of renewed growth.
guard cell – One of a pair of cells that surround a stoma, an opening in the epidermis. By changing shape, the guard cells open and close the stoma.
gymnosperm – Seed plants that are not members of the Anthophyta.
gynoecium ( gynoecia) – The megasporangiate part of the flower, consisting of one or more pistils made up of carpels.
haploid – Having one complete genome; the chromosome condition resulting from meiosis and necessary for syngamy.
heterocyst – Specialized cells found in the cyanobacteria in which nitrogen fixation occurs.
heteromorphic alternation of generations – gametophyte and sporophyte generations differ in their vegetative form.
heterosporous – Producing two different forms of meiospores – megaspores and microspores.
heterothallic – Producing male and female or (+) and (-) gametes on different gametophytes, often of dissimilar appearance.
heterotrophic – Receiving nutrition by the ingestion or absorption of high-energy organic compounds produced by other organisms.
hierarchy – An ordering of groups in which larger groups encompass sets of smaller groups.
holdfast – The portion of a filamentous or parenchymatous alga that attaches it to the substrate.
homology – Similarity of appearance as a result of common descent.
homoplasy – False homology.
homosporous – Producing only a single form of meiospore.
homothallic – Producing male and female gametes or isogametes on the same gametophyte.
hydric – Wet; applied to features of plants or places where they grow.
hydroid – A water-conducting cell of a moss.
hymenium ( hymenia) – The layer of asci in an ascocarp.
hypha ( hyphae) – A filament of the mycelium or vegetative body of a fungus or similar organism.
hypocotyl – the embryo axis of a seed plant, connecting the radicle to the cotyledons and epicotyl.
hypogynous – Condition of a flower in which the sepals, petals, and stamens arise below the ovary.
imperfect flower – A flower lacking stamens or pistils.
impression fossil – The cast or mold of the surface of an organism in usually fine-grained sedimentary rocks.
incomplete flower – A flower lacking any of the four whorls or parts (sepals, petals, stamens, or pistils).
indeterminate growth – Continuation of ontogeny when an organism reaches its final adult form; characteristic of plants. See determinate growth.
indusium ( indusia) – The tissue covering the sori of some ferns.
integument – The outer multicellular layer of the ovule, which develops into the seed coat.
internode – A region of a stem between two nodes.
irregular flower – A flower with bilateral symmetry.
isogamous – Having flagellated gametes that are identical in size and structure.
isomorphic alternation of generations – gametophyte and sporophyte generations are indistinguishable except by their sexual organs.
karyogamy – Fusion of the nuclei of two gametes; part of syngamy.
karyokinesis (
karyokineses) – Nuclear division in mitosis or meiosis.
l.s. – Longitudinal (lengthwise) section.
leaf – An often flattened photosynthetic organ attached to, and produced by, a stem.
leaf gap – An interruption of a siphonostele located above the point of attachment of a leaf trace.
leaf trace – One or more vascular bundles extending from the stele of a stem into a leaf.
leptoid – A food-conducting cell of a moss.
leptosporangium ( leptosporangia) – A meiosporangium that arises from a single initial cell and forms a wall of a single layer of cells.
life cycle – A representation of all the stages of an organisms life from birth through reproduction.
lignin – A polyphenolic substance, chemically related to tannins and flavonoids, that forms a major constituent of the secondary cell wall of vascular plant cells.
locule – a chamber in a sporangium or ovary.
megasporangium ( megasporangia) -A sporangium that produces megaspores.
megaspore – A meiospore that forms a female gametophyte.
megasporocyte – A cell that undergoes meiosis to form megaspores.
megasporophyll – A sporophyll that bears megasporangia.
meiocyte – Any diploid cell that undergoes meiosis.
meiosis ( meioses) – A form of cell division of eukaryotes in which each of the four daughter cells has half as many chromosomes as the mother cell; produces meiospores in plants and gametes in animals.
meiosporangium ( meiosporangia) – A sporangium that produces meiospores.
meiospore – A spore produced as a result of meiosis.
meiosporocyte – The diploid cell that undergoes meiosis to produce meiospores.
meristem – A group of undifferentiated cells that gives rise to mature cells and organs as a plant grows; also called a bud.
mesic- Neither especially dry nor especially wet; applied to features of plants or places where they grow.
microphyll – The flattened, photosynthetic leaf-like organ of the Lycophyta.
micropyle – the opening in the integument of the ovule of a seed plant through which the pollen grains or pollen tubes pass.
microsporangium ( microsporangia) – A sporangium that produces microspores.
microspore – A meiospore that forms a male gametophyte.
microsporocyte – A cell that undergoes meiosis to form microspores.
microsporophyll – A sporophyll that bears microsporangia.
mitochondrion ( mitochondria) – The intracellular organelle that carries out oxidative respiration.
mitosis ( mitoses) – Division of the cell nucleus of eukaryotes producing daughter cells with the same chromosome number as the original cell.
monocot – A member of the Division Anthophyta, Class Liliopsida. This class is characterized by having one cotyledon.
monoecious – Seed plant sporophytes producing both seeds and pollen.
monophyletic group – A group of organisms consisting of a common ancestor and all its descendants.
mucilage – A water-holding substance made of various complex carbohydrates, found in many plant groups.
multicellular – Of organisms, consisting of more than one cell per organism, and usually exhibiting specialization of different cells for different tasks.
mycelium ( mycelia) – A mass of hyphae forming the body of a fungus.
myxamoeba ( myxamoebae) – Single amoeboid cells of a cellular slime mold (Dictyosteliomycota); these aggregate to form the reproductive structures.
node – The point on a stem where a leaf or microphyll is attached.
nomenclature – a system of names, or the rules by which a system of names is formed.
nucellus ( nucelli) – Megasporangium of a seed plant; located within the integument.
ontogeny – The developmental history of an individual, from its beginning as a single cell (zygote, meiospore, or asexual spore) or group of cells (gemma, soredium) to its mature multicellular structure.
oogamous – Having separate flagellated gametes (sperm) and sessile gametes (ova).
oogonium ( oogonia) – The female gametangium of algae and fungi, consisting of a single specialized cell in which ova are produced.
operculum ( opercula) – in mosses, the lid of the meiosporangium.
ovary – The portion of the pistil that contains the ovules.
ovule – An integumented megasporangium of a seed plant; develops into a seed.
paramylon – The storage polysaccharide of the Euglenophyta.
paraphyletic group – a group consisting of a common ancestor and some, but not all, of its descendants.
paraphysis ( paraphyses) – A hair-like structure associated with gametangia or sporangia; present in mosses, rockweeds, and some other groups.
parallel venation – Arrangement of leaf vascular bundles in parallel along the long axis of a leaf; characteristic of monocot flowering plants.
parasite – An organism that derives its nourishment from another organism, with which it lives in close association and which is harmed by the association.
parenchyma – A tissue formed by division of cells in three dimensions; also the unspecialized type of such tissue found in vascular plants.
parsimony – The principle that the simplest explanation, the one that requires the fewest hypotheses, is the one most likely to be correct.
pedicel – A stem bearing an individual flower.
peduncle – A stem bearing a group of flowers.
pellicle – A layer of elastic proteins beneath the plasmalemma of Euglenophyta.
peptidoglycan – The primary structural polymer of the cell walls of Eubacteria and Cyanobacteria.
perfect flower – A flower with both stamens and pistils. sepals and petals may or may not be present.
perianth – Collectively, the calyx and the corolla.
peristome – A ring of inward-directed teeth surrounding the opening of a moss capsule. The peristome teeth move in response to humidity, thus facilitating spore dispersal.
perithecium ( perithecia) – Flask-shaped, partially closed ascocarp containing asci on its inner surface.
permineralization – Slow replacement of most or all of the organic material in a fossil with mineral crystals (usually silicate).
petal – A modified leaf, usually colored, forming a part of the corolla of a flower; occurs within the sepals (calyx).
petiole – The basal cylindrical stalk of a leaf.
petrifaction – See permineralization.
phloem – The vascular tissue that transports food materials in the plant body.
phycobilin – A water-soluble photosynthetic accessory pigment of the Rhodophyta and cyanobacteria.
phylogeny – Genealogy of species; the pattern of ancestry and descent of species in evolution.
pistil – The seed-producing organ of a flower, composed of one or more carpels.
pith – The inner tissue of most stems and some roots.
plasmodium ( plasmodia) – The multinucleate mass of protoplasm that constitutes the vegetative body of Myxomycota.
plasmogamy – Fusion of the cytoplasm of two gametes; part of syngamy.
plastid – A general name for chloroplasts, used especially for chloroplasts that are not green.
plectenchyma – A three-dimensional tissue formed of tightly packed filaments.
plesiomorphy – A character state already present in the ancestral species of a group under study.
polar nucleus – In the female gametophyte of Anthophyta, one of two nuclei that fuse with a sperm nucleus to form the triple fusion nucleus.
pollen – Male gametophyte of seed plants, consisting of a generative cell containing the tube nucleus and generative nucleus, and several (or no) prothallial cells.
pollen tube – The structure formed by germinating pollen that absorbs nutrients, and in some groups carries the sperm cells to the eggs.
pollination – Arrival of the pollen grain at the stigma of flowering plants, or at the micropyle of other seed plants.
polyphyletic group – A group of organisms not including the common ancestor of all members of the group.
primordium (
primordia) – a group of cells that in the normal course of events will develop into a specific mature structure or organ.
prokaryote – An organism without membrane-bound organelles, and with DNA organized in a single naked circular strand, rather than in chromosomes.
protostele – The simplest type of stele, consisting of a single column of vascular tissue.
prothallium ( prothallia) – The gametophyte of a fern; any small gametophyte.
pyrenoid – In hornworts and Chlorophyta, a region of the chloroplast involved in starch formation.
radicle – The embryonic root of a seed plant.
receptacle – The terminal part of the pedicel to which the flower parts (sepals, petals, stamens, pistils) are attached.
recombination – Formation of new combinations of genes as a result of the sexual process.
regular flower -a flower with radial symmetry.
resin duct – In seed plants, a tube-like extracellular space lined with resin-producing cells and filled with resin.
reticulate venation – Arrangement of leaf vascular bundles in a small network; characteristic of some Gnetophyta and dicot flowering plants.
rhizoid – A hairlike unicellular or filamentous absorbing and anchoring structure of organisms in the Kingdom Plantae. Root hairs are a type of rhizoid.
rhizome – An underground stem usually horizontally oriented and sometimes specialized for food storage.
root – A vascularized organ of plants that grows into the substrate.
saprophyte – A plant or microorganism that obtains its nourishment from dead organic matter, such as most fungi and bacteria and a few non-photosynthetic flowering plants.
seed – A multicellular structure containing the embryo of a seed plant, ordinarily with stored food, the whole protected by a seed coat.
seminal root – A root of a vascular plant that arises from the radicle or the zone of lateral root formation.
sepal – An outermost sterile leaflike part of a flower.
seta ( setae) – The stalk that bears the capsule of the sporophyte of a moss or liverwort. Any bristle-like structure.
sexual phase – The portion of an organism's life cycle devoted to sexual reproduction.
sexual reproduction – Formation of offspring though syngamy or meiosis.
sheath – The flattened base of a leaf that wraps around a stem.
shoot – A portion of a plant consisting of a stem and its attached leaves.
siphonostele – A stele consisting of a cylinder of vascular tissue surrounding a pith; the cylinder may be interrupted by parenchyma-filled leaf traces.
sister taxa – Monophyletic taxa that are each others closest relatives, i.e., they share an immediate common ancestral species.
sorus ( sori) – A cluster of meiosporangia on the sporophylls of ferns.
sperm – The male gamete.
spermatangium ( spermatangia) – In gametophytes of the Rhodophyta, the structures that form spermatia; equivalent to antheridium.
spermatium ( spermatia) – Small, nonmotile, male gamete produced in the Rhodophyta.
spermatocyte – The diploid cell that undergoes meiosis to form sperm.
spermatogenous tissue – groups of (usually haploid) cells that turn into sperm cells.
sporangium ( sporangia) – A unicellular or multicellular container in which spores are borne.
sporangiophore – A stem or stem-like structure bearing a sporangium.
spore – A unicellular dispersible reproductive structure. Some spores are also resistant to environmental extremes.
sporocyte – The diploid cell that undergoes meiosis to form meiospores.
sporogenous – Spore-producing.
sporophyll – A specialized leaf or leaf-like structure that bears meiosporangia.
sporophyte – A diploid organism arising from a zygote; produces meiospores by meiosis.
sporopollenin – The inert polymerized carotenoid that forms the outer cell wall of meiospores in the Kingdom Plantae.
spur shoot – A lateral shoot with short or nonexistent internodes, sometimes bearing reproductive structures or fascicles of leaves.
stamen – The pollen-producing structure in a flower, consisting of a filament and an anther.
stele – The vascular tissue of a root, leaf, or stem, taken as a unit.
stem – The vascularized above-ground supportive portion of a plant, and below-ground structures with the same anatomy and development.
stipe – The petiole of a fern frond; the stalk of a basidiocarp.
stoma ( stomata) – An opening in the epidermis of a plant controlled by two guard cells.
strobilus ( strobili) – A cone; a compact group of meiosporangium-bearing structures.
suberin – A waterproofing material secreted by cells of endodermis or periderm.
synangium ( synangia) – a structure formed of two or more cohering sporangia.
synapsis ( synapses) – Pairing of homologous chromosomes in meiosis.
syngamy – The union of gametes to form the zygote; fertilization.
tapetum ( tapeta) – A special tissue surrounding the microsporocytes in the anthers of Anthophyta.
tautology – see circular reasoning.
taxon ( taxa) – a group of organisms in a taxonomic hierarchy that have affinity to one another.
tepal- An element of a perianth that is not clearly either a sepal or a petal.
tetrad – A group of four meiospores.
tetragonal tetrad – A tetrad in which the meiospores are arranged in a square.
tetrahedral tetrad – A tetrad in which the meiospores are arranged in a tetrahedron.
tetraspore – In the Rhodophyta, the meiospore.
tetrasporophyte – In the Rhodophyta, the second diploid generation, produced by a carpospore and giving rise to tetraspores.
thallus ( thalli) – Any plant body that is formed of parenchyma or plectenchyma but is not well-differentiated into organs.
tracheid – A water-cunducting cell of a vascular plant.
trilete mark – The three-branched ridge formed by the flattened facets of a meiospore from a tetrahedral tetrad.
triple fusion nucleus – In the Anthophyta, the triploid nucleus that results from fusion of one sperm nucleus with both polar nuclei.
tube nucleus – In seed plant pollen, the nucleus that directs growth of the pollen tube.
unaltered fossils – fossils which retain more or less their original chemical and structural composition; most commonly shells of calcite (mollusks) or silica (diatoms).
unicellular – Of organisms, consisting of one cell per organism.
vascular bundle – A strand of vascular tissue running through surrounding tissue such as parenchyma.
vascular plant – A plant that produces vascular tissue.
vascular tissue – Collectively, xylem and phloem.
xanthophyll – A class of fat-soluble photosynthetic accessory pigments.
xeric – Dry; applied to features of plants or places where they grow.
xylem – The vascular tissue that transports water in the plant body; the functioning cells are dead at maturity.
zoospore – A ciliated or flagellated spore.
zoosporangium ( zoosporangia) – A sporangium that produces zoospores.
zygospore – The resistant multinucleate zygote of the Zygomycota.
zygote – The diploid cell that is produced by fusion of ovum and sperm (syngamy).