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brome mou, lesser soft brome, lopgrass, soft brome, soft chess

Arizona brome

Habit Plants annual or biennial. Plants annual; tufted.
Culms

2-70 cm, erect or ascending.

30-90 cm tall, to 3 mm thick, erect.

Sheaths

retrorsely pilose, sometimes mostly glabrous, throats sometimes with hairs;

auricles absent;

ligules 1-4 mm, usually glabrous, obtuse, erose;

blades 8-18 cm long, 3-9 mm wide, flat, sparsely pilose on both surfaces or the abaxial surfaces glabrous.

Panicles

1-13 cm long, 1-4 cm wide, erect, usually ovoid, open, becoming dense, occasionally reduced to 1 or 2 spikelets;

branches shorter than the spikelets, ascending to erect, straight or almost so.

12-25 cm, somewhat contracted or open;

lower branches shorter than 10 cm, 2-3(5) per node, initially erect to ascending, spreading at maturity, with 1-2 spikelets variously distributed.

Spikelets

(11)14-20(23) mm, lanceolate, terete to moderately laterally compressed;

florets 5-10, bases concealed at maturity;

rachilla internodes concealed at maturity.

18-25 mm, elliptic to lanceolate, strongly laterally compressed, with 4-8 florets.

Glumes

pilose or glabrous;

lower glumes 5-7 mm, 3-5-veined;

upper glumes 6.5-8 mm, 5-7-veined;

lemmas 6.5-11 mm long, 3-5 mm wide, lanceolate, chartaceous, antrorsely pilose to pubescent, or glabrous proximally or throughout, 7-9-veined, lateral veins prominently ribbed, rounded over the midvein, hyaline margins abruptly or bluntly angled, not inrolled at maturity, apices acute, bifid, teeth shorter than 1 mm;

awns 6-8 mm, usually arising less than 1.5 mm below the lemma apices, straight to recurved at maturity;

anthers 0.6-1.5 mm.

subequal, smooth or scabrous;

lower glumes 8-12.5 mm, 3-veined;

upper glumes 9.5-14 mm, 7-veined, about as long as the lowest lemma;

lemmas 9.5-14 mm, lanceolate, laterally compressed, prominently 7-veined, strongly keeled at least distally, glabrous or pubescent distally or throughout, marginal hairs, if present, longer than those elsewhere, apices entire or with acute teeth shorter than 1 mm;

awns 6-13 mm, sometimes slightly geniculate;

anthers 0.4-0.5 mm.

Caryopses

equaling or shorter than the paleas, thin, weakly inrolled to flat.

Lower

sheaths densely, often retrorsely, pilose;

upper sheaths pubescent or glabrous;

ligules 1-1.5 mm, hairy, obtuse, erose;

blades 2-19 cm long, 1-4 mm wide, abaxial surfaces glabrous or hairy, adaxial surfaces hairy.

2n

= 28.

= 84.

Bromus hordeaceus

Bromus arizonicus

Distribution
from FNA
AK; AR; AZ; CA; CO; CT; DE; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MO; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; WA; WI; WY; HI; AB; BC; LB; NB; NS; NT; ON; QC; YT; Greenland
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; NV; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Bromus hordeaceus is native to southern Europe and northern Africa. It is weedy, growing in disturbed areas such as roadsides, fields, sandy beaches, and waste places, and can be found in many locations in the Flora region, with the exception of the central Canadian provinces and most of the southeastern United States. Its origin is obscure. Ainouche et al. (1999) reviewed various suggestions, and concluded that at least one of its diploid ancestors may have been an extinct or undiscovered species related to B. caroli-henrici, a diploid species.

The four subspecies are usually morphologically distinct. Ainouche et al. (1999), however, found no evidence of genetic differentiation among them.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Bromus arizonicus grows in dry, open areas and disturbed ground of the southwest, usually below 2000 m. Its range extends from California and southern Nevada into Arizona, New Mexico, and northern Mexico.

Stebbins et al. (1944) demonstrated that, like Bromus carinatus var. carinatus, B. arizonicus obtained three of its genomes from B. catharticus or a close relative, but the remaining three genomes are not homologous with those in B. carinatus, probably being derived from a species in a section other than Ceratochloa. The small anthers of B. arizonicus strongly suggest that most seed is produced by selfing.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Lemmas (7)8-11 mm long, usually pubescent or pilose.
→ 2
2. Awns more than 0.1 mm wide at the base, straight, erect; culms (3)10-70 cm long
subsp. hordeaceus
2. Awns less than 0.1 mm wide at the base, often divaricate or recurved at maturity; culms 15-25(60) cm long
subsp. molliformis
1. Lemmas 6.5-8(9) mm long, glabrous or pubescent.
→ 3
3. Culms (3)10-70 cm long; panicles up to 10 cm long, usually with more than 1 spikelet; lemmas usually glabrous; caryopses usually as long as the paleas; habitat various
subsp. pseudothomineii
3. Culms 2-16 cm long; panicles 1-3 cm long, often reduced to 1 spikelet; lemmas pubescent or glabrous; caryopses shorter than the paleas; plants of maritime or lacustrine sands
subsp. thotninei
Source FNA vol. 24, p. 232. FNA vol. 24, p. 201.
Parent taxa Poaceae > subfam. Pooideae > tribe Bromeae > Bromus > sect. Bromus Poaceae > subfam. Pooideae > tribe Bromeae > Bromus > sect. Ceratochloa
Sibling taxa
B. aleutensis, B. anomalus, B. arenarius, B. arizonicus, B. arvensis, B. berteroanus, B. briziformis, B. carinatus, B. caroli-henrici, B. catharticus, B. ciliatus, B. commutatus, B. danthoniae, B. diandrus, B. erectus, B. frondosus, B. grandis, B. hallii, B. inermis, B. japonicus, B. kalmii, B. laevipes, B. lanatipes, B. lanceolatus, B. latiglumis, B. lepidus, B. madritensis, B. maritimus, B. mucroglumis, B. nottowayanus, B. orcuttianus, B. pacificus, B. polyanthus, B. porteri, B. pseudolaevipes, B. pubescens, B. pumpellianus, B. racemosus, B. ramosus, B. richardsonii, B. riparius, B. rubens, B. scoparius, B. secalinus, B. sitchensis, B. squarrosus, B. sterilis, B. suksdorfii, B. tectorum, B. texensis, B. vulgaris
B. aleutensis, B. anomalus, B. arenarius, B. arvensis, B. berteroanus, B. briziformis, B. carinatus, B. caroli-henrici, B. catharticus, B. ciliatus, B. commutatus, B. danthoniae, B. diandrus, B. erectus, B. frondosus, B. grandis, B. hallii, B. hordeaceus, B. inermis, B. japonicus, B. kalmii, B. laevipes, B. lanatipes, B. lanceolatus, B. latiglumis, B. lepidus, B. madritensis, B. maritimus, B. mucroglumis, B. nottowayanus, B. orcuttianus, B. pacificus, B. polyanthus, B. porteri, B. pseudolaevipes, B. pubescens, B. pumpellianus, B. racemosus, B. ramosus, B. richardsonii, B. riparius, B. rubens, B. scoparius, B. secalinus, B. sitchensis, B. squarrosus, B. sterilis, B. suksdorfii, B. tectorum, B. texensis, B. vulgaris
Subordinate taxa
B. hordeaceus subsp. hordeaceus, B. hordeaceus subsp. molliformis, B. hordeaceus subsp. pseudothomineii, B. hordeaceus subsp. thotninei
Synonyms B. mollis B. berteroanus var. excelsus
Name authority L. (Shear) Stebbins
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