Muhlenbergia diversiglumis Trin.

Muhlenbergia diversiglumis Trin. Mem. Acad. vSt.-Petersb. 6-:
298 (reprint 52). 1841.
Muhlenbergia Trinii Foum.; Hemsl. Biol. Centr. Am. Bot. 3: 543. 1885; Mex. PI. Gram. 84. 1886. (Based on M. diversiglumis Trin.)
Annual; culms very slender, delicate, several-noded, branching at all the nodes, spreading, lax, 20-50 cm. long, the nodes pilose; sheaths sparsely to rather densely papillose-pilose, mostly shorter than the internodes; ligule less than 0.5 mm. long; blades flat, lax, pilose on both surfaces, usually 2-5 cm. long, 0.5-2 mm. wide; panicles numerous, terminal and axillary, narrow, loose, mostly 1-sided, the filiform axis flexuous, the capillary scabrous branches simple, spreading or reflexed, disarticulating just above the base with the appressed subsessile spikelets attached, the lower branches somewhat distant, bearing 2—5 spikelets, the upper approximate, with two spikelets; glumes 0.2-0.3 mm. long, broad, irregularly dentate, the first glume of the terminal spikelet usually bearing a scabrous awn, 1-7 mm. long; lemma at first subterete, expanding toward maturity, scabrous on the back, pilose at base, usually ciliate on the margin toward the summit, 3-5 mm. long, tapering into a slender scabrous awn 5-15 mm. long, the tip of the lemma sometimes with a pair of slender teeth at the base of the awn; palea narrow, scabrous, the nerves extending into slender awns.
Type locality: Porto Pedro. Mexico (Karwinsky) .
Distribution: Rocky or sterile soil, southern Mexico (Michoacan, Morelos, Jalisco).

Sprawling annuals. Culms 16–50 cm tall, decumbent, rooting at the lower nodes; nodes retrorsely pilose; internodes smooth or scabridulous. Leaf sheaths 1.5–8.5 cm long, sparsely or densely pilose, hairs to 3 mm long, papillose-based; ligules 0.5–0.8 mm long, membranous, apex truncate, erose; blades 2–6 cm long, 1.5–4 mm wide, flat, bases distinctly narrowed to the junction with the sheath, surfaces scabridulous and sparsely pilose, hairs papillose-based. Panicles 6–10.5 cm long, 2.0–4.5 cm wide, secund, open; primary branches 0.8–3.5 cm long, secund, spreading at right angles or somewhat reflexed usually lying to one side with 2–5 spikelets; secondary branches not developed; pedicels 1–5 mm long, scabrous or shortly pilose, hairs papillose-based; disarticulation at the base of the primary branches where there is a weak and contorted stipe. Spikelets 4–8 mm long, dimorphic with respect to the glumes, proximal spikelets on each branch almost sessile; glumes of proximal spikelets on each branch subequal, 0.2–0.7 mm long, orbicular, truncate, often erose or irregularly toothed, unawned; glumes of distal spikelets on each branch markedly unequal; lower glumes to 8 mm long, 1-veined, acute, usually awned, awns 0.5–3 mm; upper glumes orbicular, acute, sometimes awn-tipped; lemmas 4.0–7.6 mm long, linear to broadly lanceolate, light greenish, smooth or scabrous, usually with greenish veins, apices acuminate, awned, awns 6–19 mm long, usually straight, scabrous; paleas 3.7–6.8 mm long, narrowly lanceolate, coarsely papillate or almost smooth, 2-keeled, the veins prominent, scabrous, greenish, sometimes extending as minute awns, acuminate; anthers 0.4–0.8 mm long, yellowish. Caryopses 1.8–3 mm long, oblong-ovoid, flattened, brownish. 2n = 20.

The species is native to North America, Central America, Colombia, Venezuela, Ecuador, Peru, and Argentina.