Brachypodium distachyon (L.) P.Beauv., Ess. Agrostogr. 101, 155, 156 (1812).

Bromus distachyos L.,; Trachynia distachya (L.) Link, Hort. Berol. 1: 42 (1827) ?

Vegetative form. Annual, erect or geniculate, caespitose. Leaves scattered along the culms. Culms 7-37(-50) cm high, branched above, 2-4 noded. Mid-culm nodes hairy, exposed, not pigmented, constricted. Mid-culm internodes hollow, glabrous, terete. Young shoots intravaginal. Leaves non-auriculate. Basal leaf sheaths keeled, terete (?), glabrous or papillose, with midrib prominent (but ribbed), with margins free, chartaceous, ciliate (on outer margin). Ligule 0.4-2 mm long, not lobed, decurrent, membranous, ciliolate, obtuse or truncate, entire or lacerate, abaxially hairy. Collar obscurely puberulous. Distinct callus at blade-sheath junction absent. Leaf blades joining the sheath gradually, flat, linear, 25-130 mm long, 0.9-3.5 mm wide; adaxially scabrous to adaxially puberulous (the longer hairs antrosely curved), shallowly grooved; abaxially scabrous to abaxially puberulous or abaxially pubescent (long hairs sparse), with midrib prominent; with margins scabrous or with margins scabrous and with margins ciliate, apices acute (the margins inrolled), flat. Prophyll 6-15 mm long, glabrous.

Reproductive organization. Plants bisexual. Rudimentary spikelets absent. Incomplete spikelets absent. Inflorescence of chasmogamous spikelets.

Inflorescence. Inflorescence a raceme (spike-like), green, erect, symmetrical, fully exserted. Main inflorescence axis 55-162 mm long. Peduncles 47-117 mm long, glabrous, ridged. Rachides 8-45 mm long, straight, slightly hollowed, glabrous. 1-5 spikelets on the rachis. Rachis angles scabrous to puberulous. Spikelets distichous, erect, partially embedded in the rachis (side on to the rachis), narrowly spreading (c. appressed).

Hermaphrodite (`perfect') spikelets. Hermaphrodite spikelets sessile to subsessile, 15-30 mm long, c. 6 mm wide, slightly laterally compressed, elliptic or obovate, not disarticulating as a separate unit, disarticulating above the glumes. Pedicels c. 0.9 mm long, erect, thick, puberulous, straight. Glumes two per spikelet, dissimilar (size only), unequal in length, lateral to the rachis, shorter than the florets, approximately half the proximal lemma in length. Lower glume c. 2/3s the length of the upper glume, triangular, 4.3-6.8 mm long, 0.4 mm wide, coriaceous, dorsally rounded, acute, entire, muticous, margin membranous, margin smooth or margin ciliolate (hairs sparse and obscure); 5(-7) veined, veins prominent, midvein scaberulous (and laterals); intercostal regions puberulous. Upper glume narrowly ovate, 6-8.5 mm long, 0.6 mm wide, coriaceous, dorsally rounded, acute, entire, muticous, margin membranous, margin ciliolate (hairs sparse and obscure); 7-11 veined, veins prominent, midvein scaberulous (and laterals); intercostal regions puberulous. Rudimentary florets distal to the hermaphrodite florets. Incomplete florets absent. Hermaphrodite florets 6-14 per spikelet. Rachilla disarticulating between the florets, disarticulating directly below the florets, straight (flattened), segments 1.7-2.1 mm long (flattened), papillose to scabrous, elongated between all florets, apically prolonged; prolongation 0.4 mm long, terminated by a rudimentary floret. Callus present, blunt, 0.2 mm long, glabrous. Lemma similar in firmness to the glumes, dorsally compressed, narrowly ovate (dorsally elliptic), 8.5-10.2 mm long, 1.1 mm wide (dorsally 1.3-1.5), coriaceous, not keeled, acute, entire; apiculate or awned. Lemma margins ciliolate. Lemma 7 veined. Lemma veins not confluent apically, prominent, the laterals raised and the marginals raised, scaberulous, with the hairs on all the veins, with the hairs extending the length of the veins; intercostal regions scaberulous, the hairs over the entire dorsal surface. Awns 1, median. Median awn shorter than the body of the lemmas or about as long as the body of the lemmas or much longer than the body of the lemmas (but relatively longer in upper florets), (1-)4.5-15 mm long, 1 veined, terete (subterete), straight or curved, scabrous. Palea fully developed, slightly shorter than the lemmas (3/4-7/8ths), thinner than the lemmas, tightly clasped by the lemmas, narrowly elliptic, 7.2-8.3 mm long, 1.3 mm wide, membranous (+), 2-keeled, keels wingless, obtuse (broadly), entire, margin ciliolate (upper 1/3); 2 veined, veins ciliate (hairs stiff, broad, translucent); intercostal regions puberulous. Lodicules 2, free, hyaline (with a dorsal wing of tissue), ovate, acute, ciliolate, with entire margins, glabrous or pubescent, the hairs dense. Stamens 3. Anthers 1-1.1 mm long, yellow, basally 2-lobed (c. 1/4). Ovary broadly obovoid (in outline, but flattened), pubescent to hispid, with the hairs only at the apex (erect). Styles 2, apical, free to their bases.

Fruit. Fruit strongly adhering to palea, oblong, laterally compressed, 6.4 mm long, 1.1-1.3 mm wide, deeply furrowed, pubescent to hispid, with dense hairs, the hairs confined to a terminal tuft, with a fleshy apex. Hilum 5-5.5 mm long, linear, at the base. Embryo 1.2-1.5 mm long (ovate), not waisted, with an epiblast; endosperm hard.

Abaxial leaf blade epidermis. Leaf anatomical data recorded.

Costal/intercostal zonation conspicuous to inconspicuous; the intercostal zones bordering the midrib up to 20 cells wide; epidermis differentiated into long- and short-cells; long-cells different in shape costally and intercostally (costal long-cells somewhat narrower with tessellate walls, intercostal long-cells with gently undulating walls); long-cells of similar wall thickness costally and intercostally.

Microhairs absent.

Crown cells present. Prickles present; intercostal, costal, and marginal; antrorse and retrorse; fairly uniform in size and form, or variable in size and form; of two types. Prickle bases paired with a short-cell (costally), or not paired with a short-cell (intercostally). Costal prickles along all zones; frequent in their files. 6 prickles per field in the costal zones either side of the midrib. Bases of the costal prickles longer than the width of an intercostal long-cell; barbs of the costal prickles about as long as the bases. Intercostal prickles in the astomatal files; 30 prickles per field in the intercostal zones bordering the midrib. Bases of the intercostal prickles about as long as the width of an intercostal long-cell to longer than the width of an intercostal long-cell; about as long as the stomata; barbs of the intercostal prickles about as long as the bases to up to twice as long as the bases. Macrohairs present; costal; readily distinguishable from prickles; unicellular; robust; with thickened walls; infrequent and irregularly dispersed; more than twice as long as an intercostal long-cell. Macrohair bases one-celled.

Intercostal long-cells fairly constant in shape (interstomatal long-cells somewhat shorter). Mid-intercostal long-cells markedly elongated; rectangular; long-cell walls slightly undulating to moderately undulating; end walls vertical. Papillae absent.

The costal zones all histologically similar; costal short-cells occurring sporadically in the files of long-cells as mixtures of solitaries, pairs or short rows. Costal cork-cells similar in shape to the silica cells. Costal silica bodies present and perfectly developed; throughout the costal zones; horizontal-crenate, horizontal-sinuous, cuboid, and horizontal dumb-bells (short); the dumb-bells with rounded ends, or with flattened ends, or with indented ends. The isthmuses of the dumb-bells short; wide.

Intercostal short-cells infrequent (most being replaced by prickle (hook) bases); silica bodies imperfectly developed, or present and conspicuous; silica bodies horizontal-nodular and horizontal dumb-bells.

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 2; bordering the costae. Stomata 24-27-30 m long; with guard-cells overlapped by the interstomatals. Subsidiaries dome-shaped. The domes of medium height (truncated).

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

Transverse section of the leaf blade. Lamina mid-zone in transverse section open; more or less flat; with ribs both adaxially and abaxially; the adaxial and abaxial ribs opposite one another. Adaxial furrows slight; wide. Depth of adaxial furrow/width of lamina 0.24. Adaxial furrows between all the vascular bundles. Adaxial ribs more or less constant in size, or irregular in size (those over the main bundles slightly larger); round topped; opposite all vascular bundles, or opposite major vascular bundles only (only). Vascular bundles in the mid-lamina 26; 1 per rib. Abaxial furrows absent, or present between the vascular bundles (though slight). Abaxial ribs opposite all the vascular bundles (but very slight), or opposite major vascular bundles only; smaller than adaxial ribs.

Midrib pronounced in outline; adaxially raised and pointed; 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 without a protoxylem cavity; with an enlarged protoxylem vessel; with sclerosed phloem. Midrib without colourless tissue adaxially; without lacunae. The lamina symmetrical on either side of the midrib.

Mesophyll chlorenchyma non-radiate; loosely packed to 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 present in discrete groups. The bulliform groups situated between vascular bundles. The bulliform groups without contiguous colourless mesophyll cells; small to large; simple, fan-shaped (of irregularly shaped cells). Abaxial epidermis of bulliform-like epidermal cells.

Outlines of primary vascular bundles more or less circular to more or less elliptical; 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 nowhere forming `figures', or forming I's. Outlines of lower order vascular bundles more or less circular to conspicuously angular. Lower order vascular bundles with adaxial sclerenchyma, or without adaxial sclerenchyma; with abaxial sclerenchyma, or without abaxial sclerenchyma; the adaxial sclerenchyma when present, forming girders; the abaxial sclerenchyma when present, forming girders; the combined girders of the lower order vascular bundles forming I's; the smallest vascular bundles lacking sclerenchyma. The adaxial sclerenchyma of the mid-lamina all associated with vascular bundles.

Cytology. 2n = 10, or 28, or 30 (?).

Common name. False Brome.

Distribution. Introduced. Tasmania, New South Wales, Victoria, Western Australia, and South Australia. World distribution: Mediterranean.

Ecology. Mesophytic; in open habitats. Uncommon in dry disturbed areas. Flowers Oct. Fruits Nov.

Vouchers. Specimens examined morphologically: S.A.: E of Murray Bridge, 23 Oct. 1943, R.L.Crocker (CANB). Vic.: Boort Flora Reserve, 25 Nov. 1985, A.C.Beauglehole 82803 (CANB!, MEL); Mt Jeffcott Flora Reserve, 17 km ENE Donald P.O., 23 Oct. 1979, A.C.Beauglehole 65243 & Donald History Group (CANB!, BRI, MEL, DHG). Tas.: Queens Domain, Hobart, Nov. 1929, L.Rodway (HO).

Material examined anatomically: CPI plots, Canberra. 7615, RSBS 126. S.A.: E of Murray Bridge, 23 Oct. 1943, R.L.Crocker (CANB). Vic.: Boort Flora Reserve, 25 Nov. 1985, A.C.Beauglehole 82803 (CANB!, MEL); Mt Jeffcott Flora Reserve, 17 km ENE Donald P.O., 23 Oct. 1979, A.C.Beauglehole 65243 & Donald History Group (CANB!, BRI, MEL, DHG).

Classification. Pooideae; Poodae; Brachypodieae; section Trachynia (Link) Nyman in Tutin (1980).

The genus occupies an isolated position with some resemblance to the Triticeae and Bromeae, but is often placed in an independent tribe.

References. Morphology: Wheeler et al. (1990) p. 131; Morris (1991) p. 107-108; Jacobs & Hastings (1992) ms p. 180; Clayton & Renvoize (1986) p. 150; Tutin (1980) p. 190. Cytology: Tutin (1980) p. 190.

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