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The grass genera of the world

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

Gymnachne L. Parodi

~ Rhomboelytrum, Chascolytrum

Habit, vegetative morphology. Perennial; caespitose. Culms 25–40 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear; narrow; flat, or rolled (subconvolute); not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; truncate, or not truncate; 1.5–2 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous.

Inflorescence. Inflorescence paniculate; contracted; spicate to more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.

Female-fertile spikelets. Spikelets 4–6.7 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous). Hairy callus present. Callus short; blunt.

Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; hairless; scabrous; pointed to not pointed; awnless; carinate; similar. Lower glume longer than half length of lowest lemma; 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets (if present) merely underdeveloped; awnless.

Female-fertile florets 3–6. Lemmas lanceolate; similar in texture to the glumes; not becoming indurated; incised; briefly 2 lobed; not deeply cleft; awnless, or mucronate (in the notch); hairless; glabrous; carinate to non-carinate; without a germination flap; (1–)3(–4) nerved. Palea present; relatively long; tightly clasped by the lemma; minutely apically notched; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Palea keels wingless; hairy. Lodicules present; 2; free; membranous; glabrous; not toothed; not or scarcely vascularized. Stamens 1. Anthers about 0.6 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small (1.5 mm long); fusiform; longitudinally grooved; somewhat trigonous. Hilum short. Embryo small; with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals smaller, narrower, more regularly rectangular); of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls (these conspicuously pitted). Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; mostly in cork/silica-cell pairs (a few solitary, and a few short rows); silicified. Intercostal silica bodies crescentic. Costal short-cells conspicuously in long rows and neither distinctly grouped into long rows nor predominantly paired (some costae with long rows and high concentrations of silica bodies and only occasional interrrupting prickles, other costae with predominently short rows). Costal silica bodies horizontally-elongated crenate/sinuous (these predominating, but variable in lenght and shape to approach panicoid forms), or ‘panicoid-type’ (some unambiguously referable to these); when panicoid type, cross shaped, or dumb-bell shaped, or nodular.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma (in places); without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (round topped). Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (a large group in every furrow); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the primaries); forming ‘figures’ (the larger bundles with slight I’s). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Calothecinae. 1–2 species.

Distribution, phytogeography, ecology. Chile.

References, etc. Leaf anatomical: studied by us - G. koelerioides (Trin.) Parodi.

Special comments. Nomenclatural and taxonomic confusion involves this genus and Rhomboelytrum. This morphological description includes R. berteroanum = G. jaffuelii or G. filiformis.

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.’.