Plants annual or perennial; cespitose. Culms (2)5-65 cm, herbaceous, usually rooting at the lower nodes; nodes and internodes glabrous. Leaves cauline; sheaths open, usually shorter than the internodes, mostly glabrous but long-ciliate at the edges of the collar; ligules membranous, truncate, ciliate; blades usually flat, margins ciliate. Inflorescences terminal, exceeding the upper leaves, narrow, cylindrical panicles; branches 0.5-5 mm, resembling burs, with 2-5 spikelets; disarticulation at the base of the branches. Spikelets crowded, attached individually to the branches, with 1 floret; proximal spikelet(s) bisexual, larger than the distal spikelet(s); terminal spikelets often sterile. Glumes unequal; lower glumes absent or minute, veinless, membranous; upper glumes usually exceeding the florets, 5-7-veined, with 5-7 longitudinal rows of straight or uncinate spinelike projections; lemmas 3-veined; paleas 2-veined, hyaline, membranous. x = 10. Name from the Greek tragos, he-goat.

Tragus has seven species, all of which are native to the tropics and subtropics of the Eastern Hemisphere; four have been introduced into the Flora region. The genus is easily recognized by the spinelike projections on the upper glumes. The number of veins in the glume should be determined by examining the adaxial surface, where they appear as green lines.

1.   Tragus berteronianus Schult.
Spike Burgrass

Plants annual. Culms (2)3.5-45 cm. Ligules 0.5-1 mm; blades (0.5)0.7-8.5 cm long, 1.2-5 mm wide, glabrous. Panicles (1)2-13 cm long, (3)4-8 mm wide; rachises pubescent; branches (0.5)0.7-2.7 mm, pubescent, with 2(3) spikelets, axes occasionally extending past the distal spikelets; proximal internodes 0.2-0.6(0.7) mm, shorter than the second internodes. Proximal spikelets (1.8)2-4.3 mm; second spikelets (0.8)1-3.9 mm, sometimes sterile. Lower glumes 0.1-0.6 mm, membranous, minutely pubescent; upper glumes 1.8-4.3 mm, minutely pubescent, 5-veined, rarely with 1-2 additional veins adjacent to the midvein; glume projections (4)6-14, in 5 rows, (0.2)0.3-1 mm, uncinate; lemmas (1.5)1.8-3.1 mm, sparsely pubescent on the back, midveins occasionally excurrent to 0.6 mm; paleas (1.3)1.5-2.4 mm; anthers 3, 0.4-0.6 mm, yellow, occasionally purple- or green-tinged. Caryopses (0.9)1.2-2 mm long, 0.4-0.8 mm wide. 2n = 20.

Tragus berteronianus is native to Africa and Asia, and is now established in Arizona, New Mexico, and Texas. It was collected in Maine, Massachusetts, New York, and Virginia in the nineteenth century, and Virginia in 1959.

2.   Tragus australianus S.T. Blake
Australian Burgrass

Plants annual. Culms 10-45 cm. Ligules 0.5-1 mm; blades (0.7)3.5-7 cm long, (1.5)2-4 mm wide, surfaces glabrous. Panicles (4.5)6-13.5 cm long, 7-9 mm wide; rachises pubescent; branches 0.7-1.2 mm, pubescent, with 2(3) spikelets, axes rarely extending past the distal spikelets; proximal internodes 0.6-1 mm, usually 2-3 (or more) times longer than the second internodes. Proximal spikelets 3.1-3.5 mm; second spikelets 2.7-3.3 mm. Lower glumes absent or to 0.4 mm, glabrous; upper glumes 3.1-3.5 mm, minutely pubescent, 5-veined; glume projections 7-10, in 5 rows, 0.2-0.8 mm, uncinate; lemmas 2.4-2.6 mm, sparsely pubescent on the back, midveins sometimes excurrent to 0.2 mm; paleas 2-2.2 mm; anthers 3, 0.4-0.5 mm, yellow. Caryopses 1.2-1.5 mm long, 0.6 mm wide. 2n = unknown.

Tragus australianus is native to Australia, where it becomes established rapidly on disturbed or bare soil after summer rains. In the Western Hemisphere, it is known from Berkeley and Florence counties, South Carolina, and Argentina.

3.   Tragus heptaneuron Clayton
Seven-Veined Burgrass

Plants annual. Culms 15-41 cm. Ligules 0.5-1 mm; blades 2.5-7 cm long, 3-5 mm wide, glabrous. Panicles 4-9.5 cm long, 7-9 mm wide; rachises pubescent; branches 0.5-1 mm, pubescent, with 2(3) spikelets, axes not extending past the distal spikelets; proximal internodes 0.5-0.8 mm, longer than the second internodes. Spikelets bisexual; proximal spikelets 3-3.5 mm; second spikelets 2.9-3.3 mm. Lower glumes absent or to 0.4 mm, glabrous; upper glumes 3-3.5 mm, minutely pubescent, 7-veined; glume projections 6-9, in 7 rows, 0.1-0.6(1) mm, uncinate; lemmas (2)2.3-2.7 mm, sparsely pubescent on the back; paleas 2.1-2.3 mm; anthers 3, 0.3-0.6 mm, yellow. Caryopses (1.2)1.4-1.6 mm long, 0.6 mm wide. 2n = unknown.

Tragus heptaneuron is native to tropical Africa, but it has been collected in Florence County, South Carolina.

4.   Tragus racemosus (L.) All.
Stalked Burgrass

Plants annual. Culms 5-40 cm. Ligules 0.5-1.3 mm; blades (0.5)1-5.5 cm long, 1.5-4 mm wide, glabrous. Panicles (1.5)2-11 cm long, 7-13 mm wide; rachises pubescent; branches 2.1-4.8 mm, pubescent, with (2)3-5 spikelets, axes extending past the distal spikelets; proximal internodes 0.5-1.8 mm, longer than second internodes. Proximal spikelets 3.8-6.6 mm; second spikelets (2.3)2.9-6.6 mm; third and fourth spikelets 0.8-4.2 mm; distal spikelets sterile. Lower glumes 0.7-1.1 mm, glabrous or minutely pubescent; upper glumes 3.8-6.6 mm, 7-veined, minutely pubescent; glume projections 6-11, in (5)6-7 rows, (0.2)0.6-1.3 mm, usually uncinate; lemmas 3.2-4 mm, sparsely pubescent on the back, midveins occasionally excurrent to 4 mm; paleas 2.3-3.1 mm; anthers 3, 0.6-0.8 mm, yellow. Caryopses 1.7-2.3 mm long, 0.6-0.8 mm wide. 2n = 40.

Tragus racemosus is native from the Mediterranean region to southwest Asia, but now grows in the United States, primarily in Cochise and Pima counties, Arizona. It was collected in Maine, Pennsylvania, New York, and North Carolina in the late nineteenth century, but does not appear to be established in these states. Reports for New Mexico and Texas appear to reflect confusion with T. berteronianus.