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The grass genera of the world

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

Maltebrunia Kunth

~ Potamophila

Habit, vegetative morphology. Erect perennial; stoloniferous. Culms 30–150 cm high (?); herbaceous; not scandent; unbranched above. Leaves not basally aggregated; auriculate (with sheath auricles adnate to the ligule); without auricular setae. Leaf blades lanceolate to ovate; broad; 15–50 mm wide; flat; usually pseudopetiolate; cross veined (?), or without cross venation (in M. leersioides). Ligule an unfringed membrane; not truncate (toothed). Contra-ligule absent.

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

Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.

Female-fertile spikelets. Spikelets unconventional (owing to the reduced glumes, cf. Oryza); 7–10 mm long; lanceolate; lightly compressed laterally; disarticulating above the glumes (i.e. above their vestiges); with only a short stipe above the sterile lemmas. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus short; blunt.

Glumes present to absent (vestigial); two; minute (reduced to a bilobed annulus); more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; joined; awnless. Lower glume 0 nerved. Upper glume 0 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2; epaleate; sterile. The proximal lemmas subulate; exceeded by the female-fertile lemmas (about 1/5 to 1/10 the length of the spikelet); less firm than the female-fertile lemmas (thinly membranous).

Female-fertile florets 1. Lemmas ovate-oblong or elliptic, acute, the margins clasping the lateral nerves of the palea; not becoming indurated (firmly chartaceous); entire; pointed; awnless; hairy (with thin, appressed white hairs), or hairless; carinate; without a germination flap; 5 nerved; with the nerves non-confluent. Palea present; relatively long (equalling the spikelet); tightly clasped by the lemma; entire (narrow, acute); awnless, without apical setae; textured like the lemma; not indurated; several nerved (three nerved); one-keeled. Palea keels wingless. Lodicules present; 2; free; membranous (but relatively substantial, in the material seen); glabrous. Stamens 6. Anthers about 3–4 mm long (relatively long, linear); not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2 (plumose).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal (mostly in the stomatal zones, adjoining the costae - not to be confused with the abundant, bulbous prickle bases). Intercostal papillae not over-arching the stomata (for the most part); several per cell (small, round, scattered on the interstomatals). Long-cells similar in shape costally and intercostally (the costals rather smaller); of similar wall thickness costally and intercostally (of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse). Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common (but absent from the mid-intercostal regions). Subsidiaries non-papillate; dome-shaped to triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (hard to observe in the material seen); in cork/silica-cell pairs and not paired; seemingly not silicified. Large bulbous-based prickles with reduced points, abundant both costally and intercostally. Costal short-cells conspicuously in long rows (in some files), or predominantly paired (in other files). Costal silica bodies oryzoid.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous; having complex vascularization (there being an abaxial arc of three with a median one adaxially, in the material seen); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms constituting most of the adaxial epidermis, in very wide fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most of the bundles); forming ‘figures’ (I’s with the smaller bundles, ‘anchors’ with the large ones). Sclerenchyma all associated with vascular bundles.

Special diagnostic feature. Female-fertile lemma not as in Rhynchoryza (q.v.).

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Oryzeae. Soreng et al. (2015): Oryzoideae; Oryzeae; Zizaniinae. 3–5 species.

Distribution, phytogeography, ecology. Gabon, Tanzania, Madagascar.

Shade species; glycophytic.

References, etc. Morphological/taxonomic: Hubbard 1962. Leaf anatomical: studied by us - M. leersioides Kunth.

Special comments. Fruit data wanting. Illustrations. • M. leersioides: Kunth (1835), Rev. des Graminées t.3. • M. leersioides, opened spikelet in close-up: this project. Maltebrunia leersioides. Vestigial glumes not apparent beneath two short, subulate, empty proximal lemmas; one female-fertile floret (lemma at left, palea at right), six stamens.

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.’.