Diplopogon R.Br.
Including Dipogonia P. Beauv.
Sometimes referred to Amphipogon
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; a fringe of hairs.
Reproductive organization. Plants bisexual, 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 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).
Taxonomy. Arundinoideae (?); Amphipogoneae.
Distribution, ecology, phytogeography. 1 species; Western Australia.
Australian. South-West Australian.
References, etc. Morphological/taxonomic: Macfarlane and Watson 1980. Leaf anatomical: this project.
Illustrations. • General aspect and spikelet
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
