1. Brachiaria eruciformis (Sm.) Griseb. (signalgrass)
Pl. 160 j,
k
Plants with C4 photosynthesis, annual, usually
with stolons, forming clumps. Flowering stems 10–60 cm long, spreading in the
basal portion and rooting at the lower nodes, the tips ascending, densely hairy
at the nodes. Leaf sheaths hairy, the ligule 0.5–1.0 mm long, a short line or
band of hairs. Leaf blades 1–9 cm long, 2–6 mm wide, usually flat, hairy, the
base rounded or abruptly narrowed. Inflorescences 3–9 cm long, narrow panicles
with the 3–15 primary branches unbranched and consisting of spikelike racemes,
these with a spikelet at the tip (a thickened, cuplike base remaining after the
spikelet disarticulates). Spikelike racemes 5–25 mm long, appearing 1‑sided
with the 5 to numerous spikelets in 2 rows, these not subtended by bristles or
spines, disarticulating below the glumes (and sometimes also between the
florets). Spikelets 2.0–2.6 mm long, without a cuplike ring or knoblike disk at
the base. Lower glume 0.3–0.5 mm long, broadly oblong‑ovate, wrapped
around the spikelet base, bluntly pointed to nearly truncate at the tip, awnless,
1‑nerved, glabrous. Upper glume 1.6–2.0 mm long, about as long as the
rest of the spikelet, elliptic, not inflated, bluntly to sharply pointed at the
tip, awnless, 5‑nerved, hairy. Lowermost floret sterile, the lemma
1.6–2.0 mm long, about as long as the rest of the spikelet, elliptic, sharply
pointed at the tip, awnless, 5‑nerved, hairy. Fertile floret with the
lemma 1.3–1.8 mm long, oblong‑elliptic, rounded at the tip, which is not
differentiated from the body, awnless, nerveless or obscurely nerved, glabrous,
shiny, smooth, thickened and relatively hard (usually somewhat bonelike) at
maturity, the margins not thinner or lighter colored, noticeably wrapped around
the palea and fruit, but not enclosing the free palea tip. Paleas glabrous,
about as long as and similar in texture to the lemma. Anthers 0.5–1.0 mm long.
Fruits 1.2–1.5 mm long, oblong‑elliptic in outline, yellowish brown to
dark brown. 2n=18, 36. September–October.
Introduced, known from a single collection from Stone County (native of Europe, Asia, and Africa; escaped from cultivation nearly worldwide,
mostly in tropical and subtropical regions). Banks of creeks.
In some parts of the world, this species is cultivated as a
lawn grass. It is an uncommon escape in the United States. The specimen upon
which Steyermark (1963) based his report for Missouri could not be located
during this study, but it seems unlikely to have been misdetermined. It may be
part of a set of collections made by Steyermark during the period of about
1955–1957 that disappeared after he left the Field Museum.