2. Bromus diandrus Roth (ripgut grass, great brome)
Pl. 138 a,
b; Map 557
Plants annual, forming tufts. Flowering stems 30–80 cm long,
erect or ascending, usually glabrous. Leaves 3–8 per stem. Leaf sheaths of
lower leaves overlapping, soft‑hairy, the tip strongly concave (V‑shaped),
without auricles. Leaf blades 5–25 cm long, 3–6 mm wide, hairy, dull on the
undersurface. Inflorescences open panicles with numerous spikelets, the
branches spreading to drooping at maturity, the stalks of the spikelets longer
than the spikelets. Spikelets (including the awns) 50–70 mm long, slightly
compressed laterally, with 4–7 florets. Lower glume 13–22 mm long, narrowly
lanceolate, 1‑ or 3‑nerved, glabrous but sometimes roughened along
the midnerve. Upper glume 20–32 mm long, narrowly lanceolate, 3‑ or 5‑nerved,
glabrous but sometimes roughened along the midnerve. Lemmas with the body 22–30
mm long, narrowly lanceolate, rounded on the back, the margins not inrolled at
maturity, mostly 7‑nerved, glabrous but roughened along the nerves and
margins, the apical teeth 1–4 mm long, the awn 35–65 mm long, straight or
nearly so. Paleas shorter than the lemmas. Anthers 0.7–1.5 mm long. Fruits
10–12 mm long, circular in cross‑section to somewhat flattened or
slightly V‑shaped, the longitudinal groove narrow and shallow. 2n=56.
Introduced; known only from Jackson County and St. Louis
(native of Europe and adjacent Asia and Africa; naturalized in the western
U.S.). Railroads and disturbed areas.
Steyermark (1963) and several other authors referred to this
species as B. rigidus Roth, but that name corresponds to a different,
closely related taxon not found in Missouri (Gould, 1975). It differs from B.
diandrus in its stiffly ascending inflorescence branches and shorter
spikelet stalks. The long awns of both taxa can injure the soft mouthparts,
nostrils, and eyes of livestock.