Bromus diandrus Roth, Bot. Abh. Beobacht. 44 (1787).

T: not designated.

Vegetative form. Annual. Culms 35-62 cm high, 3 noded or 5 noded. Mid-culm nodes glabrous. Mid-culm internodes hollow, glabrous. Leaves non-auriculate. Basal leaf sheaths not keeled, terete, puberulous to pilose, with margins connate, in lower 2/3s, hyaline, ciliate. Ligule 1.5-2.5 mm long, hyaline, smooth, obtuse to truncate, erose, abaxially glabrous. Collar puberulous to pilose. Leaf blades flat, linear, 170-175 mm long, 4.5-5 mm wide; adaxially pilose; abaxially pilose; with margins ciliate.

Reproductive organization. Plants bisexual. Incomplete spikelets absent. Inflorescence of cleistogamous spikelets.

Inflorescence. Inflorescence a raceme to a panicle, open to contracted. Main inflorescence axis 280 mm long. Peduncles 130 mm long. Rachides 65-150 mm long, subterete, pubescent to pilose. Rachis angles puberulous to pilose. Primary inflorescence branches spreading to divaricate. Spikelets 1-2(-3) on a typical ultimate inflorescence branch, on first order branches.

Hermaphrodite (`perfect') spikelets. Hermaphrodite spikelets pedicellate, 28-30 mm long, slightly laterally compressed or not noticeably compressed. Pedicels 5-28 mm long. Glumes two per spikelet, free, similar, subequal. Lower glume c. 3/4s the length of the upper glume, narrowly oblong, 15.75-19 mm long, 0.75-1 mm wide, membranous to chartaceous, keeled to dorsally rounded, long acuminate to acute, muticous, margin hyaline to margin membranous, margin smooth; 1 veined, acropetally midvein papillose to midvein scabrous; intercostal regions glabrous. Upper glume narrowly oblong, 24-25 mm long, 1.5-2 mm wide, membranous to chartaceous, keeled to dorsally rounded, long acuminate to acute, muticous, margin hyaline to margin membranous, margin smooth; 3 veined or 5 veined, veins obscure, midvein scabrous; intercostal regions glabrous. Incomplete florets present, distal to the hermaphrodite florets. Rachilla straight, acropetally minutely scabrous to puberulous, elongated between all florets, apically prolonged. Callus present, pointed, 1 mm long, glabrous or puberulous (trichomes rigid; restricted to narrow acropetal and lateral zones), hairs 0.25 mm long. Lemma similar in firmness to the glumes, narrowly ovate to narrowly elliptic, 19-25 mm long, 2 mm wide, membranous to chartaceous, acropetally keeled, long acuminate to acute, emarginate, 2 -lobed, awned. Lemma margins minutely scabrous. Lemma 7 veined. Lemma veins confluent towards the apex, obscure, acropetally connected by obscure transverse veins, scabrous, with the hairs on all the veins, with the hairs extending the length of the veins; intercostal regions scabrous, the hairs over the entire dorsal surface. Awns 1, median. Median awn much longer than the body of the lemmas, 36-53 mm long, 3 veined, subapical, scabrous. Palea fully developed, slightly shorter than the lemmas, slightly thinner than the lemmas or similar in texture to the lemmas, tightly clasped by the lemmas, narrowly oblong or narrowly elliptic to narrowly obovate, 13-15 mm long, 1.5 mm wide, membranous, 2-keeled, keels wingless, acuminate or obtuse, entire; 2 veined, veins scabrous; acropetally intercostal regions scabrous to intercostal regions puberulous (minute and isolated). Lodicules 2, free, hyaline, acute, toothed to with entire margins, with margin divisions terminal, glabrous. Stamens 3; filaments 2.5-3 mm long. Anthers 1.5 mm long or 3-3.5 mm long, basally 2-lobed. Ovary with a conspicuous apical appendage, pilose, with the hairs only at the apex. Styles 2, free to their bases. Distal incomplete florets 3 per spikelet, neuter (some, however, have poorly developed stamens), awned, shortly paleate or epaleate.

Abaxial leaf blade epidermis. Leaf anatomical data recorded.

Costal/intercostal zonation conspicuous; the intercostal zones bordering the midrib 24-42 cells wide; epidermis differentiated into long- and short-cells; long-cells different in shape costally and intercostally; long-cells of similar wall thickness costally and intercostally.

Microhairs absent.

Crown cells absent. Prickles present (as macrohairs); intercostal and marginal; antrorse and retrorse; fairly uniform in size and form. Prickle bases not paired with a short-cell. Intercostal prickles in the astomatal files. Bases of the intercostal prickles longer than the width of an intercostal long-cell; shorter than the stomata, or longer than the stomata; barbs of the intercostal prickles more than twice as long as the bases. Macrohairs present; intercostal; intergraded with long prickles; unicellular; lax to robust; with thickened walls; sparse but frequent; more than twice as long as an intercostal long-cell. Macrohair bases one-celled; attached at cuticle only; uniform in mode of insertion.

Intercostal long-cells fairly constant in shape. Mid-intercostal long-cells markedly elongated; fusiform; inflated; long-cell walls straight; end walls vertical and angled; the intercostal long-cell walls not conspicuously pitted. Papillae absent.

The costal zones all histologically similar; costal short-cells conspicuously in long rows, or solitary. Costal silica bodies present and perfectly developed; throughout the costal zones; horizontal-crenate and horizontal-smooth.

Intercostal short-cells absent; silica bodies absent.

Stomata common; present in all the intercostal zones; restricted in distribution within intercostal zones; arranged in definite rows. Stomatal rows in the widest intercostal zones 4-5; evenly dispersed. Stomata 66-67-72 m long; with guard-cells overlapped by the interstomatals. Subsidiaries dome-shaped to parallel-sided. The domes low.

Photosynthetic pathway and related features. C3. XyMS+. The PBS sheaths of the primary lateral vascular bundles interrupted. Mestome sheath single; complete.

Transverse section of the leaf blade. Lamina mid-zone in transverse section open; more or less flat to V-shaped. Width of lamina across a primary vascular bundle 180-198.5-240 m. Lamina mid-zone in transverse section exhibiting adaxial ribs only. Adaxial furrows slight. Adaxial furrows between all the vascular bundles. Adaxial ribs more or less constant in size to irregular in size; round topped; opposite all vascular bundles. Vascular bundles in the mid-lamina 24-25; 1 per rib. Abaxial furrows absent.

Midrib pronounced in outline; adaxially raised and rounded; prominent abaxially; tissue layout similar to that of other primary vascular bundles. Vascular bundles in the mid-lamina region of the midrib 1. The median vascular bundle with a protoxylem cavity; with an enlarged protoxylem vessel; with sclerosed phloem. Midrib without colourless tissue adaxially (but the adaxial linking sclerenchyma always contains large, relatively thin-walled cells); without lacunae. The lamina symmetrical on either side of the midrib.

Mesophyll chlorenchyma non-radiate; tightly packed. Mesophyll without lacunae; without any obvious adaxial palisade; without `circular cells'; not traversed by columns of colourless cells; without arm cells; without fusoids. Bulliforms absent as discrete groups but the epidermis extensively bulliform. Abaxial epidermis of bulliform-like epidermal cells. Abaxial epidermal cell walls not thickened, or thickened. The cells irregular in shape, or regular in shape, ovoid.

The major vascular bundles interspersed with minor bundles; outlines of primary vascular bundles more or less circular; primary vascular bundles centrally situated. Primary lateral vascular bundles with adaxial sclerenchyma; with abaxial sclerenchyma; the adaxial sclerenchyma forming girders; the abaxial sclerenchyma forming girders; the combined girders forming I's. Outlines of lower order vascular bundles more or less circular. Lower order vascular bundles centrally situated; with adaxial sclerenchyma, or without adaxial sclerenchyma; without abaxial sclerenchyma; the adaxial sclerenchyma when present, forming strands, or forming girders; the smallest vascular bundles lacking sclerenchyma. The adaxial sclerenchyma of the mid-lamina all associated with vascular bundles.

Cytology. 2n = 56.

Distribution. Introduced; commonly adventive. Tasmania, New South Wales, Australian Capital Territory, Victoria, Western Australia, and South Australia.

Vouchers. Specimens examined morphologically: R.B.Barker 169: Lower Marshes, Jordan R. (Tas.); xi.1964; Fl.; CANB - R.D.Pearce 261: S. of Sandergrove Siding towards Milang (S.A.); 22.ix.1982; Fr.; ADW, BRI, CANB, NSW - R.Pullen 4309: C.S.I.R.O. grounds, Black Mtn, Canberra (A.C.T.); 22.xi.1968; Fr; BAA, CANB, DELHI, TNS, UNIV - R.J.Cranfield s.n. CANB 330420: Burns Beach (W.A.); 20.x.1979; Fr.; CANB, PERTH - R.Hardigan s.n. NSW 127682: Nundle (N.S.W.); 11.xii.1971; Fr.; CANB, NSW.

Material examined anatomically: R.D.Pearce 261 SA CANB; R.B.Barker 169 Tas CANB; D.E.Symon 3534 SA CANB (listed as aff. diandrus by Murray).

Classification. Triticodae; Bromeae.

This species and B. rigidus are difficult to distinguish. The best characters traditionally are rather trivial, and, for Australian material, have been reviewed by ???? (19??) who identify such things as the shape of the callus scar and ?? as being of taxonomic utility. During the course of the current study further questions have arisen concerning the composition of what is considered to be B. diandrus in Australia. These problems relate mainly to the number of lower and upper glume veins, which have been traditionally used (e.g. by Tutin et al.) to distinguish sects. Genea and Pnigma from sects. Bromus and Ceratochloa (it should be noted, however, that Hubbard (1984) describes this species as having 1-3 veined lower glumes, and 3-5 veined upper glumes). A number of B. diandrus collections possess 2-3 veined lower glumes and 3-5 upper glumes which, according to Tutin et al., would place them within the sect. Bromus/Ceratochloa alliance rather than sect. Genea - work is continuing (There may be some B. sterilis mixed in with this description?).

References. Illustrations: bromus02.gif

Cite this publication as:
C.M. Weiller, M.J. Henwood, J. Lenz and L. Watson (1995 onwards). `Pooideae (Poaceae) in Australia - Descriptions and Illustrations'. URL http://muse.bio.cornell.edu/delta/
Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993) should also be cited.

References and Acknowledgements