Plants annual or perennial but short-lived; tufted. Culms 30-100
cm, geniculate. Sheaths compressed, glabrous or sparsely pilose; ligules
0.5-1.4 mm; blades 3-28 cm long, (1)3-7.2 mm wide, glabrous or sparsely
long-pilose adaxially. Panicles 3-5(8.5) cm; fascicles 5.5-10.2
mm long, 2.5-5 mm wide, imbricate, ovoid to globose, glabrous or sparsely to
moderately pubescent; outer bristles, when present, mostly flattened;
inner bristles 8-40 (rarely more), 2-5.8 mm long, 1-2 mm wide, fused
at least 1/2 their length, forming a distinct cupule, the distal portions usually
diverging from the cupule at multiple, irregular intervals, sometimes diverging
at more or less the same level, ciliate at the base, pubescent, stramineous
to mauve or purple, flattened. Spikelets 2-4 per fascicle, 3.5-5.9 mm,
glabrous. Lower glumes 1-3.3 mm; upper glumes (2.8)3.5-5 mm, 5-7-veined;
lower florets sometimes staminate; lower lemmas 3-5(5.9) mm, 5-7-veined;
lower paleas sometimes reduced or absent; anthers 1.3-1.6 mm;
upper lemmas 3.5-5(5.8) mm; anthers 0.5-1.2 mm. Caryopses
about 2.5 mm long, 1-2 mm wide, ovoid. 2n = 34 (32).
Cenchrus spinifex is common in sandy woods, fields, and waste places
throughout the southern United States and southwards into South America. It
may be more widespread than shown in the northern portion of the contiguous
United States because it has often been confused with C.
tribuloides. Cenchrus spinifex differs from C. tribuloides
in its glabrous or less densely pubescent fascicles, narrower inner bristles,
and larger number of bristles. It has also been confused with C.
longispinus, but differs in having shorter spikelets, fewer bristles
overall, wider inner bristles, and outer bristles that are usually flattened
rather than usually terete.
Annual to short-lived perennial, slender, 3-10 dm; sheaths glabrous or sparsely villous at the summit; blades 2-18 cm נ2-6 mm; bur 5.5-10 נ2.5-5 mm (spines excluded),
usually rather shortly hairy, cleft on 2 sides, with mostly 8-40 basally flattened, retrorsely barbed spines 2-5 mm; spikelets 3.5-6 mm, 2-4 per bur, exserted at the tip; 2n=34. Sandy soil; trop Amer., n. to se. Va., Ark., and Kans.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.