Flora of New Zealand Series

Type species: B. secalinus L.

Annuals or perennials, tufted or occasionally rhizomatous. Leaf-sheath often pubescent; margins connate. Ligule membranous. Leaf-blade flat. Inflorescence an open or contracted panicle, or rarely a raceme. Spikelets 2-many-flowered, ± laterally compressed; florets chasmogamous or cleistogamous; disarticulation above glumes and between lemmas. Glumes unequal or subequal, acute or shortly awned; lower 1-7-nerved, upper 3-9-nerved. Lemma rounded or keeled, 5-13-nerved, bidentate, awned from near apex; awn straight, bent or recurved, or 0. Palea usually < lemma, 2-keeled, keels ciliate or scabrid. Lodicules 2, entire, connate below, glabrous. Stamens (2)-3. Ovary with a terminal, hairy appendage and styles inserted laterally. Fig. 12.

SYNOPSIS

• A.
• • Annuals or rarely biennials
  • 1. Sect. BROMUS. 
  • • Spikelets ovate or lanceolate, terete or ± compressed, tapering to tip. Lower glume 3-5-nerved, upper 5-7-nerved. Lemma rounded; awn o, or > lemma:
    • 1. arenarius, 3. commutatus, 5. hordeaceus,japonicus var. vestitus, 9. racemosus,secalinus
  • 2. Sect. GENEA. 
  • • Spikelets cuneiform, broader at tip. Lower glume 1-nerved, upper 3-nerved. Lemma rounded; awn > lemma:
    • 4. diandrus, 8. madritensis,rubens, 12. sterilis, 13. tectorum
• B.
• • Perennials
  • 3. Sect. BROMOPSIS. 
  • • Spikelets parallel-sided, terete. Lower glume 1-(3)-nerved, upper 3-nerved. Lemma rounded or weakly keeled; awn < lemma or 0:
    • erectus, 6. inermis
  • 4. Sect. Ceratochloa. 
  • • Spikelets strongly compressed, narrowed to tip. Lower glume 3-5-nerved, upper 5-9-nerved. Lemma strongly keeled; awn < lemma or 0:
    • 2. brevis,catharticus, 7. lithobius, 10. sitchensis, 11. stamineus, 14. valdivianus, 15. willdenowii

c. 150 spp. of temperate regions especially in Northern Hemisphere. Naturalised spp. 15; transient spp. 5.

Bromus L. has been variously divided into six sections [Smith, P. Notes Roy. Bot. Gard. Edinb. 30: 361-375 (1970)], seven subgenera [Stebbins, G. L. Bot. Jahrb. Syst. 102: 359-379 (1981)], or five subgenera [Tsvelev, N. N. Grasses of the Soviet Union 1: 298-343 (1976)]. No consensus has been reached on the treatment of the complex but many authors agree with Smith, P. (op. cit.) that sectional rank is "most appropriate for the infrageneric elements within Bromus s.l."

In an expanded checklist of naturalised species of Bromus and their first records in New Zealand, Forde, M. B. and Edgar, E. N.Z. J. Bot. 33: 35-42 (1995) discussed the nomenclature of species in Bromus sect. Ceratochloa, in particular of South American B. catharticus, B. valdivianus and B. willdenowii; they concluded that B. willdenowii Kunth was the correct name for prairie grass, rather than B. catharticus or B. unioloides; they accepted B. brevis (Nees) Steud. as specifically distinct from B. catharticus. They also agreed with Muñoz-Schick, M. Fl. Parque Nac. Puyehue 488-489 (1980) that B. valdivianus was distinct from B. stamineus.

Stebbins, G. L. (op. cit.) discussed the levels of polyploidy within Bromus. Species in sect. Bromus, sect. Bromopsis and sect. Genea are mainly diploid (2 n = 14) and tetraploid (2 n = 28). Within sect. Ceratochloa the South American species are hexaploid (2 n = 42), whereas North American species are octoploid (2 n = 56) and 12-ploid (2 n = 84).