4. Leptochloa panicoides (J. Presl) Hitchc. (Amazon sprangletop)

Pl. 150 e, f; Map 610

Diplachne panicoides (J. Presl) McNeill

Diplachne halei Nash

Plants annual, forming tufts. Flowering stems 40–110 cm long, erect or ascending. Leaf sheaths rounded on the back or the lowermost keeled, glabrous or rarely slightly roughened, the ligule 2–4 mm long, uneven along the margin. Leaf blades 4–20 cm long, 4–10 mm wide, glabrous or somewhat roughened, especially on the margins. Inflorescences 12–35 cm long, with 20–90 branches, these 2–8 cm long. Spikelets 3.5–5.0 mm long, moderately flattened, with 4–7 florets. Lower glume 0.9–1.9 mm long, narrowly lanceolate, sharply pointed at the tip. Upper glume 1.6–2.3 mm long, ovate, sharply pointed at the tip. Lemmas 2.2–3.0 mm long, narrowly elliptic to ovate, sharply pointed at the tip, sometimes minutely notched, awnless or with a minute, sharp point, keeled. Anthers 0.6–0.8 mm long. Fruits 1.1–1.4 mm long, elliptic to obovate in outline, slightly flattened. 2n=20. August–October.

Scattered in the Mississippi Lowlands Division (southeastern U.S. west to Missouri and Texas; Mexico, Central America, South America). Bottomland forests and banks of rivers, usually in sandy soils; also ditches, moist roadsides, rice fields, and moist, open, disturbed areas.

Steyermark (1963) included this species based on a single specimen from New Madrid County. However, since that time it has become somewhat more common and widespread in southeastern Missouri. Gould (1975) considered L. panicoides to represent a Brazilian native that is a widespread introduction in North America, but this does not seem likely, particularly in view of the fact that the taxon originally was described by Presl in 1830 from material collected prior to that time in Mexico.