1. Bromus commutatus Schrad. (hairy chess, meadow brome)
Pl. 139 e,
f; Map 556
Plants annual, forming tufts. Flowering stems 30–120 cm
long, erect or ascending, mostly glabrous. Leaves 4–6(–10) per stem. Leaf
sheaths loosely overlapping toward the base of the stem, soft‑hairy (the
upper ones often sparsely so), the tip strongly concave (V‑shaped),
lacking a well‑defined ring of hairs on the outer surface and without
auricles. Leaf blades 6–25 cm long, 1–8 mm wide, hairy, dull on the
undersurface. Inflorescences open panicles with numerous spikelets, the
branches spreading (especially the lowermost ones) or somewhat ascending at
maturity, the stalks of the spikelets longer than the spikelets. Spikelets
10–22 mm long, slightly compressed laterally at maturity, with 4–12 florets.
Lower glume 5–7 mm long, narrowly elliptic‑lanceolate, 3(5)‑nerved,
glabrous to roughened or hairy. Upper glume 6–9 mm long, elliptic‑lanceolate,
5–9‑nerved, glabrous to roughened or hairy. Lemmas (7–)8–10 mm long,
elliptic to oblanceolate, the distance (in lemmas toward the middle of the
spikelet) from the midnerve to margin 1.5–2.5 mm at the widest point, rounded
on the back, the margins not or only slightly inrolled at maturity, with an inconspicuous,
narrow, whitened band, lightly 7(9)‑nerved, glabrous to roughened or
hairy, the apical teeth 1–2 mm long, the awn (1.5–)5–12 mm long, rarely absent,
straight or nearly so. Paleas slightly shorter than the lemmas. Anthers 0.7–1.7
mm long. Fruits 6–7 mm long, circular in cross‑section to somewhat
flattened or slightly V‑shaped, the longitudinal groove narrow and
shallow. 2n=14, 28, 56. Late May–July.
Introduced, scattered nearly throughout Missouri (native of Europe
and Asia, widely naturalized in the U.S. and Canada). Roadsides, railroads,
pastures, and open, disturbed areas.
The status of B. commutatus in North America has been
controversial. Steyermark (1963) and several other authors reduced this to a
synonym of the closely related B. racemosus, whereas most authors
studying the plants in the Old World have regarded them as separate species.
The present treatment follows those of Gereau (1987), Gleason and Cronquist
(1991), and Pavlick (1995) in accepting these as distinct species. Depauperate
or juvenile plants of this species also are very difficult to separate from B.
japonicus or B. squarrosus. In addition to the characters in the key
to species, B. commutatus differs from B. racemosus in having the
florets attached mostly 1.5–2.0 mm (vs. 1.0–1.5 mm) apart on the rachilla.