Andropogon arctatus Chapm.

Andropogon arctatus Chapm. Bot. Gaz. 3 : 20. 1878
Andropogon tetrasta-chyus distachyus Chapm. Fl. S. U. S. 581. 1860. Not.<4. distachyos "L,. 1753. Sorgum, arctatumKntitzQ, Rev. Gen. 791. 1891.
Stems 1-1.5 m. tall, branched toward the summit, the branches in I's-S's; leaf-sheaths, at least the lower ones, more or less densely appressed-hirsute at the summit; blades erect, 3 dm. long or less, up to 5 mm. wide, the upper surface rough, the lower usually densely appressed-hirsute toward the base; racemes in pairs, rarely in 3's or 4's, rather stout, dark-gray, 2.5-4 cm. long, long-exserted, the rachis of many internodes, the internodes about one half as long as the sessile spikelets, densely pubescent with long hairs; sessile spikelet linearlanceolate, 5-6 mm. long, the first scale with the margins broadly infolded, the keels hispidulous, the back glabrous and slightly concave, the callus barbed with hairs about one third as long as the scale, the second scale with the keel hispidulous and the margins ciliate, the fourth scale shortly and acutely 2-toothed, ciliate, bearing an awn 7-12 mm, long, imperfect or sometimes a little spiral at the base; pedicellate spikelet usually present, consisting of a single scale, the pedicel considerably shorter than the sessile spikelet.
Type locality : Low pine barrens, western Florida Distribution : Western Florida.

Perennials, Terrestrial, not aquatic, Rhizomes present, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stems branching above base or distally at nodes, Stem internodes solid or spongy, Stems with inflorescence less than 1 m tall, Stems with inflorescence 1-2 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades more or less hairy, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule an unfringed eciliate membrane, Ligule a fringed, ciliate, or lobed membrane, Inflorescence terminal, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence a panicle with narrowly racemose or spicate branches, Inflorescence a pan icle with digitately arranged spicate branches, Inflorescence with 2-10 branches, Inflorescence branches paired or digitate at a single node, Inflorescence branches paired racemes, V-shaped, Flowers bisexual, Flowers unisexual, Spikelets pedicellate, Spikelets sessile or subsessile, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 2 florets, Spikelets paired at rachis nodes, Spikelets in paired units, 1 sessile, 1 pedicellate, Pedicellate spikelet rudimentary or absent, usually sterile, Spikelets bisexual, Spikelets unisexual, Inflorescence disarticulating between nodes or joints of rachis, rachis fragmenting, Spikelets disarticulating below the glumes, Spikelets falling with parts of disarticulating rachis or pedicel, Spikelets conspicuously hairy , Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glumes keeled or winged, Glume surface hairy, villous or pilose, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 1 nerved, Lemma 3 nerved, Lemma glabrous, Lemma apex dentate, 2-fid, Lemma mucronate, very shortly beaked or awned, less than 1-2 mm, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn less than 1 cm long, Lemma awn 1-2 cm long, Lemma awned from tip, Lemma awn from sinus of bifid apex, Lemma awn once geniculate, bent once, Lemma margins thin, lying flat, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Stamens 1, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis.

Andropogon arctatus là một loài thực vật có hoa trong họ Hòa thảo. Loài này được Chapm. mô tả khoa học đầu tiên năm 1878.