64. Eriochloa Kunth (cup grass)
(Shaw and Webster, 1987)
Plants with C4 photosynthesis, annual (perennial
elsewhere), forming tufts or less commonly clumps. Flowering stems erect from
often spreading bases or mostly spreading, sometimes rooting at the lowermost
nodes, glabrous or hairy. Leaf sheaths glabrous or hairy, rounded on the back,
the ligule a line or band or hairs, sometimes with a minute membrane at the
base. Leaf blades usually flat, hairy or rarely glabrous. Inflorescences dense
or open panicles with several primary branches ascending, mostly unbranched,
and consisting of spikelike racemes, the racemes appearing 1‑sided, with
the spikelets occurring singly or paired along 1 side of the axis, the axis
with a spikelet at the tip. Spikelets not subtended by bristles or spines, but
with a small, cuplike ring or knoblike disk at the base (formed by fusion of
the thickened joint at the spikelet base and the reduced, modified lower
glume). Upper glume about as long as the rest of the spikelet, not inflated or
saclike at the base, rounded to sharply pointed at the tip, awnless or with a
short awn, hairy. Lowermost floret sterile, the palea absent or highly reduced,
the lemma about as long as the rest of the spikelet, awnless or with a minute,
awnlike point, hairy. Fertile (perfect) floret with the lemma slightly shorter
than that of the staminate or sterile floret, bluntly to sharply pointed at the
tip, awnless or more commonly with a short awn, nerveless or very faintly 5‑nerved,
glabrous, dull, thickened and hard (usually somewhat bonelike) at maturity, the
margins also thick, wrapped around the palea and fruit, but not enclosing the
free palea tip. Paleas glabrous, dull, thickened and hard (usually somewhat
bonelike) at maturity. Anthers 0.6–1.0 mm long. Fruits narrowly to broadly
oblong‑elliptic in outline. About 30 species, nearly worldwide, mostly in
tropical and subtropical regions.
The cuplike structure at the spikelet base is unique among Missouri grasses. In fresh plants, the cuplike base is usually yellow or a brighter
yellowish green than the rest of the spikelet, and frequently a small bead of
an oily liquid is found in it or at its tip.