Muhlenbergia microsperma (DC.) Kunth

Muhlenbergia microsperma (DC.) Kunth, Rev. Gram. 1: 64 1829.
TrichocMoa microsperma DC. Cat. PI. Hort. Monsp. LSI. 1813.
Podosaemum debile H.B.K. Nov. Gen. & .Sp. 1: 128. 1815. (Type from Ecuador.)
Podosaemum setosum H.B.K. Nov, Gen. & Sp. 1: 129. 1815. (Type from Mexico.)
Agrostis microsperma Lag. Gen. & Sp. Nov. 2. 1816. (Type grown in Botanic Garden, Madrid,
the seed from Mexico.) Trichochloa debilis R. & S. Syst. Veg. 2: 385. 1817. (Based on Podosaemum debile H.B.K.) Trichochloa setosa R. & S. Svst. Veg. 2: 386. 1817. (Based on Podosaemum seiosum H.B.K.) Muhlenbergia fasciculala Trin. Gram. Unifl. 192. 1824. (Type from North America.) Agrostis setosa Spreng. Svst. 1; 262. 1825. (Based on Podosaemum setosum H.B.K.) Not A.
setosa Miihl. 1817. Agrostis debilis Spreng. Syst. 1:262. 1825. (Based on Podoiaemam de6j7e H.B.K.) Not .4. rfe-
A:7j5 Poir. 1810. Muhlenbergia setosa Kunth. Rev. Gram. 1: 63. 1829. (Based on Podosaemum setosum H.B.K.) Muhlenbergia debilis Kunth, Rev. Gram. 1: 63. 1829. (Based on Podosaemum debile H.B.K.) Muhlenbergia purpurea Nutt. Jour. Acad. Phila. IL 1: 186. 1848. (Type from Santa Barbara
and Santa Catalina Island, California, Gambel.) Muhlenbergia ramosissima Va,sev, Bull. Torrey Club 13: 231. 1886; S. Wats. Proc. Am. Acad. 21:
443. 1886. (Type from Southwest Chihuahua, Palmer 158 in 1885.)
Annual ; culms slender, scaberulous at least below the nodes, branching at base and more or less at all the nodes, spreading, 10-70 cm. tall; sheaths more or less scaberulous, mostly shorter than the internodes; ligule thin, 1.5-2 mm. long; blades flat or loosely involute, more or less scabrous on both surfaces, mostly less than 10 cm. long, rarely longer, usually less than 1 mm. wide, sometimes as much as 3 mm. wide; panicles numerous, usually purple, terminal and axillary, narrow, 5-20 cm. long, the scabrous branches and branchlets and scabrous-pubescent pedicels spreading and somewhat implicate in anthesis, the axis angled, scabrous, the lateral pedicels comparatively stiff and stout, 1 mm. long; glumes subequal, broad, awnless, usually obtuse at tip, the second about 1 ram. long ; lemma narrow, attenuate above, scabrous, especially on the 3 rather strong nerves, 4—5 mm. long, the callus pubescent, the apex with 2 minute awned teeth ; awn slender, nearly straight, 1-3 cm. long. Cleistogamous spikelets are developed at the base of the lower sheaths, solitary or few in a fascicle in each axil, each spikelet included in an indurate-thickened, tightly rolled, narrowly conical, reduced sheath, which readily disarticulates from the plant at maturity. The glumes are wanting and the awn of the lemma is reduced but the grain is larger than that of the spikelets in the terminal inflorescence, being about the same length (2 mm.) but much thicker.
Type locality: Mexico.
Distribi'Tion; Rocky places and dry open ground, Arizona and southern California to Guatemala; also in Ecuador and Peru.

Caespitose annuals, sometimes appearing as short-lived perennials. Culms 10–80 cm tall, often geniculate at the base, slender, often striate, much branched near the base, scaberulous below the nodes; internodes 1.8–8.6 mm long, mostly scaberulous or smooth. Leaf sheaths 2.2–6.6 mm long, commonly shorter than the internodes, glabrous, smooth or scaberulous; ligules 1–2 mm long, membranous to hyaline, decurrent, margins often extended, apex truncate to obtuse; blades 3–8.5(–10) cm long, 1–2.5 mm wide, flat or loosely involute, scabrous below, strigulose above, often deciduous with age. Panicles 6.5–13.5 cm long, 1–6.5 cm wide, open and not densely flowered, often purplish; primary branches 1.6–4 cm long, ascending or diverging up to 80° from the rachises, spikelet-bearing to the base; pedicels 2–6 mm long, appressed to divaricate, antrorsely scabrous. Cleistogamouspanicles with 1–3 spikelets present in the axils of the lower sheaths. Spikelets 2.5–5.5 mm long; glumes 0.4–1.3 mm long, exceeded by the florets, 1-nerved, obtuse, often minutely erose; lower glumes 0.4–1 mm long; upper glumes 0.6–1.3 mm long; lemmas 2.5–3.8(–5.3) mm long, narrowly lanceolate, mostly smooth, scaberulous distally, lower 1/2 of the margins and midveins, the hairs 0.2–0.5 mm long, the callus hairy, apices acuminate, often bidentate, awned, awns 10–30 mm long, straight to flexuous; paleas 2.2–4.8 mm long, narrowly lanceolate, acuminate; anthers 0.3–1.2 mm long, purplish. Caryopses 1.7–2.5 mm long, fusiform, reddish-brown. 2n = 20, 40, 60.

Muhlenbergiamicrosperma occurs in Hawaii, south-western U.S.A., Mexico, Guatemala, Colombia, Venezuela, Ecuador (including the Galapagos Islands), Peru and Bolivia (Peterson and Annable 1991).

Annuals, Terrestrial, not aquatic, Stems nodes swollen or brittle, 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 hollow, Stems with inflorescence less than 1 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 disarticulating from sheath, deciduous at ligule, Leaf blades linear, Leaf blades very narrow or filiform, less than 2 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, o r conduplicate, Leaf blades mostly glabrous, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence branches more than 10 to numerous, Flowers bisexual, Spikelets pedicellate, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes shorter than adjacent lemma, Glumes 1 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma 3 nerved, Lemma glabrous, Lemma a pex dentate, 2-fid, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn 1-2 cm long, Lemma awn 2-4 cm long or longer, Lemma awn from sinus of bifid apex, Lemma awns straight or curved to base, Lemma margins thin, lying flat, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Palea present, well developed, Palea membranous, hyaline, Palea about equal to lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Muhlenbergia microsperma is a species of grass known by the common name littleseed muhly. It is native to the Americas from the Southwestern United States and California through Central America into Peru and Venezuela.

It can be found in many habitat types, including disturbed areas.

It is an annual or perennial grass growing up to 60 to 80 centimeters tall. The inflorescence is an open, spreading array of thin branches bearing small spikelets which have awns up to 3 centimeters long. Spikelets lower in the inflorescence stay within sheaths and do not bloom.

Agrostis microsperma é uma espécie de gramínea do gênero Agrostis, pertencente à família Poaceae.

Muhlenbergia microsperma là một loài thực vật có hoa trong họ Hòa thảo. Loài này được (DC.) Trin. mô tả khoa học đầu tiên năm 1824.