Cenchrus spinifex
Cenchrus gracillimus
coastal sandbur, common sandbur
slender sandbur
30-100 cm, geniculate.
20-80 cm, wiry.
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.
shorter than the internodes, keeled, usually glabrous, rarely sparsely pilose;
ligules 0.2-0.6 mm;
blades 5-25 cm long, 1-3.5 mm wide, stiff, adaxial surfaces usually glabrous, smooth or scabrous.
3-5(8.5) cm;
fascicles 5.5-10.2 mm long, 2.5-5 mm wide, imbricate, ovoid to globose, glabrous or sparesely 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.
2-6(6.8) cm;
rachis internodes 2-4 mm;
fascicles 5-13 mm long, 2-4 mm wide, not imbricate, ovoid, glabrous;
outer bristles sometimes present, flattened;
inner bristles less than 30, 3.2-6 mm long, 0.2-1 mm wide at the base, in more than 1 whorl, fused for at least 1/2 their length into a distinct cupule, diverging at irregular intervals from the cupule, somewhat flattened, spreading, purple-tipped at maturity.
2-4 per fascicle, 3.5-5.9 mm, glabrous.
1-3 per fascicle, 4-7 mm.
about 2.5 mm long, 1-2 mm wide, ovoid.
1.8-3 mm long, 1-1.5 mm wide, ovoid-elliptic.
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.
glumes 1.4-3.1 mm;
upper glumes 3.2-5.4 mm, 3-5-veined;
upper lemmas 4-6 mm, 3-5-veined;
upper florets 3.9-6.5 mm;
anthers 0.9-1.9 mm.
= 34 (32).
= 34.
Cenchrus spinifex
Cenchrus gracillimus
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Cenchrus gracillimus grows in sandy soils of open pinelands, wet prairies, and river flats of the southeastern United States and the West Indies.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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