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Published In: Species Plantarum 1: 76. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 8/6/2009)

 

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34. Bromus L. (brome, brome grass)

(Pavlick, 1995)

Plants with C3 photosynthesis, annual or perennial. Leaf sheaths closed to well above the middle, sometimes to the tip or nearly so, the ligules membranous. Inflorescences panicles or less commonly racemes. Spikelets stalked, slightly to strongly compressed laterally, with 4–30 fertile florets and usually 2 or 3 sterile florets at the tip, disarticulating above the glumes and between the florets, the rachilla noticeably zigzag. Glumes 2, usually unequal in length, herbaceous to papery, 1–9‑nerved, usually awnless. Lemmas herbaceous to papery, rounded to strongly keeled on the back, 5–13‑nerved, the tip divided into two, minute teeth, with the awn (if present) attached between the teeth. Paleas 2‑nerved, lacking awns. Stamens (1–)3, the anthers mostly orange. Fruits somewhat flattened, usually with a longitudinal groove on 1 side. About 150 species, North America, South America, Europe, Asia, Africa; mostly in temperate regions.

The few species of Bromus native to Missouri are perennial, clump‑forming species of mesic upland and bottomland forests. Most species of bromes in the state were introduced for cultivation as pasture grasses and other fodder (secondarily for erosion control). It is ironic that in some parts of the country large acreages of native grasses were replaced by species of Bromus. Although some species are excellent forage grasses, others are relatively unpalatable to livestock and became known as cheatgrass. Several species with long awns can even cause injury to the noses, eyes, mouths, and intestines of cattle and other species that attempt to graze on them. Following the widespread cultivation of bromes in temperate North America, various taxa proved weedy and invasive, particularly in disturbed habitats. As a result, some species are quite widespread and common in Missouri, sometimes at the expense of native vegetation.

 

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1 Spikelets strongly compressed laterally, the glumes and lemmas sharply keeled on the back 14 Bromus willdenowii
+ Spikelets at most slightly compressed laterally, the glumes and lemmas rounded to bluntly angled on the back, not keeled (2)
2 (1) Lower glume 1-nerved, rarely with 2 additional nerves only at the base; upper glume 3-nerved, sometimes with 2 additional, faint nerves near the margins (3)
+ Lower glume 3–5-nerved, the nerves all well developed; upper glume 5–9-nerved (9)
3 (2) Plants annual; leaves 2–6 mm wide; awns (8–)10–65 mm long, often (but in B. tectorum not always) as long as or longer than the lemmas (4)
+ Plants perennial; leaves 5–15 mm wide; awns absent or 0.5–8.0 mm long, shorter than the lemmas (6)
4 (3) Lemmas with the body 22–30 mm long, the awn 35–65 mm long 2 Bromus diandrus
+ Lemmas with the body 8–22 mm long, the awn (8–)10–30 mm long (5)
5 (4) Spikelets (including the awns) 40–50 mm long; body of the lemma 14–22 mm long, the awn 18–30 mm long 12 Bromus sterilis
+ Spikelets (including the awns) 20–35 mm long; body of the lemma 8–12 mm long, the awn (8–)10–12(–17) mm long 13 Bromus tectorum var. tectorum
6 (3) Plants with well-developed, creeping rhizomes, forming loose colonies; inflorescence branches stiffly ascending at maturity; lemmas glabrous, the awn lacking or 0.5–2.5 mm long 4 Bromus inermis
+ Plants with rhizomes lacking or very poorly developed, forming tufts or clumps; inflorescence branches spreading to drooping at maturity; lemmas sparsely to densely hairy, the awn 2.5–8.0 mm long (7)
7 (6) Leaves 8–20 per stem; leaf blades with a pair of auricles at the base; leaf sheaths truncate to slightly concave at the tip 6 Bromus latiglumis
+ Leaves 4–8(–10) per stem; leaf blades without outgrowths of tissue at the base; leaf sheaths strongly concave (V-shaped) at the tip (8)
8 (7) Leaf blades with the undersurface shiny (sometimes difficult to see when dried; also note that the shiny undersurface appears as the “upper” surface because the blade is twisted at the base); sheaths with a dense ring of hairs on the outer surface at the tip (on the side opposite the ligule); upper glume mostly 5-nerved 7 Bromus nottowayanus
+ Leaf blades with the undersurface dull; sheaths lacking a well-defined ring of hairs at the tip, although the outer surface sometimes uniformly hairy; upper glume 3-nerved 8 Bromus pubescens
9 (2) Lemmas with the body 22–30 mm long, the awn 35–65 mm long 2 Bromus diandrus
+ Lemmas with the body 6–12 mm long, the awn absent or more commonly 0.5–12.0 mm long (species often difficult to determine, especially from immature or depauperate specimens) (10)
10 (9) Inflorescences short and dense, the branches appressed-ascending, short, the stalks of the spikelets shorter than the spikelets 3 Bromus hordeaceus
+ Inflorescences longer and more open, the branches ascending to spreading or drooping, but not appressed (except sometimes when very young), longer, the stalks of the spikelets mostly longer than the spikelets (11)
11 (10) Fruits U-shaped in cross-section, the longitudinal groove broad and deep; margins of lemmas strongly inrolled at maturity, exposing the rachilla; lowermost leaf sheaths usually glabrous or nearly so 10 Bromus secalinus
+ Fruits circular in cross-section to somewhat flattened or slightly V-shaped, the longitudinal groove narrow and shallow; margins of lemmas not inrolled or only slightly inrolled at maturity, generally not exposing the rachilla; lowermost leaf sheaths moderately to densely hairy (12)
12 (11) Most of the lemmas (except sometimes the lowermost few of each spikelet) with awns noticeably curved, twisted, or abruptly bent outward, the tips mostly spreading (13)
+ Lemmas with awns straight or nearly so, ascending (14)
13 (12) Lemmas toward the middle of each spikelet relatively narrow, the distance from midnerve to margin 1.5–2.5 mm at the widest point, with an inconspicuous, narrow, whitened band along the margins 5 Bromus japonicus
+ Lemmas toward the middle of each spikelet relatively wide, the distance from midnerve to margin 2.5–3.5 mm at the widest point, with a conspicuous, broad, whitened band along the margins 11 Bromus squarrosus
14 (12) Inflorescence with the lowermost branches spreading at maturity; largest lemmas of mature spikelets 8–10 mm long; anthers 0.7–1.7 mm long 1 Bromus commutatus
+ Inflorescence with the lowermost branches ascending at maturity; largest lemmas of mature spikelets 6.5–8.0 mm long; anthers 1.5–3.0 mm long 9 Bromus racemosus
 
 
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