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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Diplopogon R.Br.

~ Amphipogon

Type species: Type: D. setaceus R.Br.

Including Dipogonia P. Beauv.

Habit, vegetative morphology. Perennial; caespitose. Culms 30–60 cm high; herbaceous; unbranched above. Culm nodes glabrous. Leaves non-auriculate. Leaf blades narrow; setaceous (and convolute); without cross venation; persistent. Ligule a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile; overtly heteromorphic (the sterile spikelets reduced to setaceous bracts).

Inflorescence. Inflorescence paniculate; contracted; capitate to more or less ovoid; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets associated with bractiform involucres (constituted by the glumes of the lowermost spikelets); not secund; shortly pedicellate, or subsessile.

Female-sterile spikelets. The sterile spikelets forming a fairly inconspicuous involucre of linear, convolute, subulate or setaceous bracts at the base of the panicle.

Female-fertile spikelets. Spikelets compressed laterally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret.

Glumes two; more or less equal (G1 being slightly longer than G2); long relative to the adjacent lemmas (exceeding them); pointed (acuminate); awned (the G1s usually being acuminate into a long straight point); non-carinate (rounded on the back); similar (lanceolate and hyaline). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas narrow bodied; convolute (below); decidedly firmer than the glumes (firmly chartaceous); not becoming indurated; incised; 3 lobed; deeply cleft; awned. Awns 3; median and lateral (the lateral lobes acuminate into short, erect, scabrid awns, the median much longer); the median different in form from the laterals; from a sinus (i.e., from between the lateral lobes); non-geniculate (but much flattened below, twisted and laterally displacing); hairless; about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein. The lateral awns shorter than the median (erect, scabrid). Lemmas hairy (with silky hairs below); non-carinate; 3 nerved. Palea present; relatively long; awned (apically 2-awned); not indurated (membranous); 2-nerved. Lodicules present; 2; free; fleshy. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small. Hilum short. Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae present. Intercostal papillae not over-arching the stomata. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent (but present adaxially); panicoid type. Stomata absent or very rare. Subsidiaries non-papillate. Intercostal short-cells common. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies tall-and-narrow and crescentic.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups; in simple fans (poorly differentiated fans, to Ammophila-type aggregations of small cells, in the furrows). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups; abaxial-hypodermal, the groups isolated (opposite the adaxial furrows).

Classification. Watson & Dallwitz (1994): Arundinoideae (?); Amphipogoneae. Soreng et al. (2015): Arundinoideae; Arundineae. 1 species (D. setaceus).

Distribution, phytogeography, ecology. Western Australia.

References, etc. Morphological/taxonomic: Macfarlane and Watson 1980. Leaf anatomical: studied by us.

Illustrations. • D. setaceus: Gardner, 1952

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 11th December 2017.’.