Digitaria insularis |
Digitaria patens |
|
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sourgrass |
Texas cottontop |
|
Habit | Plants perennial; cespitose, shortly rhizomatous, with knotty bases. | Plants perennial; cespitose, neither rhizomatous nor stoloniferous. |
Culms | 80-130 cm, erect, with densely villous cataphylls, branching from the lower and middle nodes. |
40-90 cm, erect, sometimes geniculate, not rooting, at the lower nodes. |
Sheaths | usually sparsely to densely papillose-hirsute, occasionally glabrous; ligules 4-6 mm, usually lacerate, not ciliate; blades 20-50 cm long, 10-17 mm wide, lax, smooth or scabridulous abaxially, scabridulous to scabrous adaxially. |
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Leaves | mainly cauline; basal sheaths villous; upper sheaths glabrous or sparsely to densely hirsute, hairs papillose-based; ligules (1)1.5-4 mm, entire to lacerate; blades 5-15 cm long, 1-4 mm wide, glabrous or sparsely pubescent. |
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Panicles | 20-35 cm long, 2-10 cm wide, with numerous spikelike primary branches; primary branches 10-15 cm, appressed to ascending at maturity, axes not wing-margined or with wings less than 1/2 as wide as the midribs; internodes 3-4.5(6) mm (midbranch), bearing spikelets in unequally pedicellate pairs; secondary branches rarely present; pedicels not adnate to the branches; shorter pedicels 0.7-2 mm; longer pedicels 2.5-5 mm; terminal pedicels 2-5 mm. |
with 4-10 spikelike primary branches on (4)10-18 cm rachises; primary branches 4-10 cm, usually divergent at maturity, varying to ascending, axes not wing-margined, bearing spikelets in unequally pedicellate pairs; internodes (4.5)6-15 mm (mid-branch); secondary branches rarely present; shorter pedicels 2-2.5 mm; longer pedicels 7-8 mm; terminal pedicels of primary branches 7.4-20 mm. |
Spikelets | 5.5-8.2 mm (including pubescence), 4.2-5.9 mm (excluding pubescence), narrowly ovate, acuminate. |
homomorphic, 3.7-5.8 mm (including pubescence), 2.9-4.3 mm (excluding pubescence). |
Lower glumes | 0.6-0.8 mm; upper glumes 3.5-4.5 mm, 3-5-veined, pubescent on the margins; lower lemmas 4.1-5.7 mm (exceeded 1.5-5 mm by pubescence), narrowly ovate, 7-veined, pubescent between most, sometimes all, of the veins and on the margins, veins usually obscured by a dense covering of golden-brown hairs, hairs 3-6 mm, spreading at maturity, intercostal regions on either side of the midvein glabrous or pubescent with shorter, fine, white hairs, sometimes intermixed with the golden-brown hairs; upper lemmas 3.2-4.5 mm, narrowly ovate, brown when immature, dark brown at maturity, acuminate; anthers 1-1.2 mm. |
0.3-0.5 mm; upper glumes 2.4-3.5 mm (excluding pubescence), 3-veined, densely villous, hairs 1.5-4 mm, silvery-white to purple, spreading at maturity; lower lemmas 2.8-4.2 mm (excluding pubescence), exceeding the upper lemmas by 0.8-2.2 mm, 5-veined and the veins equally spaced or 7-veined and the lateral veins closer to each other than to the central vein, margins densely villous, hairs 1.5-4 mm, silvery-white to purple, spreading at maturity, apices acuminate; upper lemmas 2.6-3.2 mm, lanceolate, brown when immature, dark brown at maturity, acuminate. |
2n | = 36. |
= 72. |
Digitaria insularis |
Digitaria patens |
|
Distribution |
AL; AZ; FL; IL; MS; TX; HI; PR; Virgin Islands
|
TX |
Discussion | Digitaria insularis grows in low, open ground of the southern United States, and extends to the West Indies, Mexico, and through Central America to Argentina. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Digitaria patens is endemic to southwestern and southern Texas and adjacent Mexico. It grows in well-drained, usually sandy, soils, often in disturbed habitats. Gould (1975) suggested that it might be an octoploid derivative of D. californica. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 25, p. 370. | FNA vol. 25, p. 368. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Trichachne insularis | Trichachne patens |
Name authority | (L.) Mez ex Ekman | (Swallen) Henrard |
Web links |