Glossary of Botanical Terms - T

T

taproot

the main, descending root of a plant with a single dominant root axis.

taxon

(plural taxa) a group or category in a system of classification, derived from the Greek prefixes taxo-, taxis- meaning arrangement.

taxonomy

the study of the principles and practice of classification.

tegmen

the inner layer of the testa (seed coat). It develops from the inner integument of the ovule.

tendril

a slender organ (modified e.g. from stem, leaf, leaflet or stipule) used by climbing plants to cling to an object.

tepal

perianth segment, either sepal or petal; usually used when all perianth segments are similar in appearance; cf. petal.

terete

circular in cross-section; more or less cylindrical.

terminal

situated at the tip or apex.

ternate

in groups of three; of leaves, arranged in whorls of three; of a single leaf, with the leaflets arranged in groups of three. See Leaf shape.

terrestrial

generally denotes of or on the ground; of habitat, on land as opposed to in water (aquatic) or on rocks (lithophytic), or other plants (epiphytic), and so on.

testa

seed coat.

tetrad

a group of four; usually means four pollen grains remaining fused together a maturity, e.g. in the Epacridaceae.

tetraspore

the asexual spore of red algae. It is so named because each sporangium produces just four spores. See Rhodophyceae.

thorn

a sharp, stiff point, usually a modified stem, that cannot be detached without tearing the subtending tissue; a spine; cf. prickle.

throat

the opening of a corolla or perianth.

thyrse

a branched inflorescence in which the main axis is indeterminate (racemose) and the lateral branches determinate (cymose).

tomentum

(adjective tomentose) a dense covering of short, matted hairs. Tomentose is often used as a general term for bearing an indumentum, but this is not a recommended use.

toothed

with a more or less regularly incised margin.

torus

see receptacle.

trademark (trade mark)

a distinctive word, picture, symbol, smell or other device or any combination or multiples of these. It must not be descriptive of the goods or services, nor can it be geographical nor a surname. Used to distinguish one trader from another, compared with PBR which protect the commercial name of a particular plant variety.

trapeziform

1. like a trapezium (a four-sided figure with two parallel sides of unequal length)

2. like a trapezoid (a four-sided figure, or quadrilateral, with neither pair of sides equal); sometimes used erroneously as a synonym for rhombic.

tree

a woody plant, usually with a single distinct trunk and generally more than 5 m tall.

triad

a group of three.

triangular

planar and with 3 sides.

tribe

a taxonomic grouping, in rank between genus and species.

trichome

in non-filamentous plants, any hair-like outgrowth from epidermis, e.g. a hair or bristle; sometimes restricted to unbranched epidermal outgrowths.

trifoliolate (or trifoliate)

a compound leaf of three leaflets, for example a clover leaf.

trigonous

triangular in cross-section and obtusely angled; cf. triquetus.

trinerved

having three nerves or veins.

triplinerved

(of leaves) having three main nerves with the lateral nerves arising from the midnerve above the base of the leaf.

triquetrous

more or less triangular in cross-section, but acutely angled (with 3 distinct longitudinal ridges); cf. trigonus.

trivial name

the second word in the two-part scientific name of an organism; cf. specific epithet.

trophophyll

a vegetative, nutrient-producing leaf or microphyll, whose primary function is photosynthesis. It is not specialized or modified for some other function. (compare: sporophyll).

trullate

ovate but angled; like a bricklayer's trowel; inverse kite-shaped; compare rhombic.

truncate

cut off squarely; with an abruptly transverse end.

trunk

the upright large main stem of a tree.

truss

a compact cluster of flowers or fruits arising from one centre; for instance, evident in many rhododendrons.

tuber

an underground storage organ formed by the swelling of an underground stem which produces buds and stores food, forming a seasonal perennating organ, for example potato; compare tuberoid.

tubercle

a small wart-like outgrowth.

tuberculate

covered in tubercles; warty.

tuberoid

an underground storage organ formed by the swelling of a root; occurs in many orchids.

tuberous

resembling a tuber; producing tubers.

tubular

with the form of a tube or cylinder.

tunic

outer covering of some bulbs and corms.

turbinate

top-shaped.

turgid

swollen with liquid; firm; compare flaccid.

tussock

a dense tuft of vegetation, usually well separated from neighbouring tussocks, for example some grasses; compare sward.

two-ranked

having leaves arranged in two rows in the same plane, on opposite sides of the branch; = distichous.

type

an item (usually a herbarium specimen) to which the name of a taxon is permanently attached, i.e. a designated representative of a plant name. Important in determining the priority of names available for a particular taxon.

type genus

in nomenclature, the genus from which the family is based.

typography

the presentation of printed matter, covering issues such as type styles (e.g. italic or roman type), underlining, emboldening and letter spacing.