taxon (plural taxa): any taxonomic entity, of whatever rank.

tendril (8 images): a slender, coiling or twining organ by which a climbing plant grasps its support.

tepal (23 images): a sepal or petal, or member of an undifferentiated perianth.

terete (1 image): cylindrical; round in cross-section.

ternate (8 images): in 3's.

tessellate: with a checkered or paving-block pattern.

testa: the seed coat, derived from the integuments of the ovule.

tetradynamous: with 4 long and 2 short stamens, as in many Brassicaceae.

thalloid: resembling or consisting of a thallus.

thallus: a plant body that is not clearly differentiated into roots, stems, and leaves.

theca: a pollen sac or locule of an anther.

thorn (5 images): a stiff, woody, modified stem with a sharp point.

throat: the orifice of a gamopetalous corolla or gamosepalous calyx, or the somewhat expanded part between the proper tube and the limb; in grasses, the upper margins of the sheath.

thyrse: an elongate, narrow, mixed panicle.

tomentose (7 images): covered with tangled or matted, woolly hairs.

tomentulose: diminutive of tomentose.

tomentum: a covering of tangled or matted, woolly hairs.

tortuose: twisted or winding (e.g., as in a dehiscing fruit).

torulose: alternately swollen and pinched (e.g., some Brassicaceae or Fabaceae fruit).

torus: the receptacle of a flower or of a head.

trailing: prostrate but not rooting.

trichome (2 images): any hairlike outgrowth of the epidermis.

trichotomous: forking in 3's.

trifid (2 images): divided or cleft into three parts.

trifoliate (2 images): with 3 leaves.

trifoliolate: with 3 leaflets.

trigonous: with 3 angles.

trilete: fern and lycophyte spores with a more or less triangular shape and a Y-shaped suture called on their germinal surface.

trilocular: with 3 locules.

trimerous: with 3 parts of a kind.

triploid: possessing three chromosome copies.

triquetrous: with 3 sharp or projecting angles.

trullate: ovate but angled; inverse kite-shaped.

truncate: with the apex (or base) transversely straight or nearly so, as if cut off.

tuber (7 images): a thickened part of a rhizome, generally at the end, serving in food storage and often in reproduction.

tubercle (4 images): a small swelling or projection.

tuberculate: bearing tubercles.

tuberous: thickened like a tuber.

tubular (10 images): with the form of a tube.

tunicate: covered or provided with sheathing leaf bases that form concentric circles when viewed in cross-section, as the bulb of an onion.

turbinate: top-shaped.

turgid: swollen.

turion (4 images): a small, bulblike vegetative offset, as in some species of Epilobium and many aquatic species.