Citation: R. Br., Prod. Fl. Nov. Holl. 182 (1810).

Derivation: Greek treis, three; odous, a tooth; the lemma is divided into 3 obtuse or acute teeth or lobes.

Synonymy: Not Applicable

Common name: Porcupine grasses, desert spinifexes.

Description:
Perennials; leaf blades long, subulate, rigid, often spreading, ending in needle-like points, forming a prickly tuft or tussock at the base of the stems; ligule a ring of hairs, usually very short.

Spikelets several-flowered, compressed laterally, the upper flowers reduced, male or empty, arranged in a narrow but rather loose panicle; glumes stiff, acute, keeled, 3- or more-nerved, subequal, persistent, shorter than the flowers; rhachilla disarticulating; lemmas stiff, rounded on the back at least in the lower half, the nerves 6-9, rarely more, arranged in 3 sets of 2 or 3 (rarely more) nerves each, with 3 lobes or 2 lobes and a central mucro; callus short, bearded; lodicules 2, free, broadly obovate, sometimes 3-lobed at the summit.

Distribution:  35 Australian species (N. T. Burbidge (1953) Aust. J. Bot. 1:121-184).

Biology: No text

Key to Species:

1. Leaf sheaths resinous	T. pungens 6.
1. Leaf sheaths not resinous
2. Spikelets not conspicuously racemose along the lateral branches
3. Lobes of the lemmas stiffly scarious and as long as or longer than the horny base; leaf sheaths more or less woolly, always woolly at the orifice
4. Lateral lobes of the lemmas obtuse or acute and glabrous except for the marginal cilia	T. basedowii 1.
4. Lateral lobes of the lemmas acuminate and softly pubescent	T. lanigera 4.
3. Lobes of the lemmas never as long as the base and may be mere indentations of the apices, not scarious unless the whole texture is thin; leaf sheath not usually woolly
5. Central nerve of the lemmas continued as a short awn between the stiffly scarious lateral lobes; palea glabrous on the back; glumes as long as or nearly as long as the spikelets	T. irritans var. irritans 2.
5. Central nerve of the lemma short in an emarginate or ragged or semitruncate apex; glumes rarely more than half as long as the spikelet, usually about as long as the lowest lemma (if longer then the lemma is not aristulate); palea hairy on the back
6. Sheaths and glumes glabrous, puberulent or scabrid
7. Glumes and lemmas stiff and more or less indurate; lateral portions of the lemmas flat and with a group of 2 or 3 distinct nerves
8. Spikelets 8-12-flowered; lemmas neatly distichous-imbricate; coastal	T. irritans var. compacta 2.
8. Spikelets 4-8-flowered; opposing lemmas closely over-lapping when young but later very loosely distichous and divaricate; inland	T. irritans var. laxispicata 2.
7. Glumes and lemmas thinly scarious; lateral nerve (or closely proximal nerves) forming a ridge above so that the lemma may appear dorsally flattened towards the apex	T. scariosa 7.
6. Leaf sheaths woolly-tomentose; glumes more or less pubescent	T. lanata 3.
2. Spikelets racemose along conspicuously alternate lateral branches of a narrow panicle	T. longiceps 5.

Author: Not yet available