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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.

Distribution, phytogeography, ecology. Western Australia.

References, etc. Morphological/taxonomic: Macfarlane and Watson 1980. Leaf anatomical: this project.

Illustrations. • D. setaceus: Gardner, 1952


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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: 13th November 2017. delta-intkey.com/grass’.

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