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The grass genera of the world

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

Megalachne Steud.

Including Pantathera Phil.

Habit, vegetative morphology. Perennial; caespitose. Culms 40–100 cm high; herbaceous. Young shoots intravaginal. Leaves not basally aggregated; distichous; non-auriculate. Sheaths glabrous. Leaf blades linear; narrow; flat, or rolled (convolute when dry); without cross venation; persistent. Ligule an unfringed membrane; not truncate (elongated, laciniate); 5–10 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.

Inflorescence. Inflorescence rather few spikeleted; paniculate; fairly open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 10–26 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present (well developed, with stiff hairs).

Glumes present; two; more or less equal; long relative to the adjacent lemmas; hairless; pointed; awned (both, or only the lower); carinate to non-carinate; very dissimilar to similar (herbaceous, linear-lanceolate, aristulate to awned). Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awned.

Female-fertile florets 2–6. Lemmas lanceolate-acuminate; similar in texture to the glumes to decidedly firmer than the glumes (subleathery); not becoming indurated; entire; awned. Awns 1; median; apical; non-geniculate; recurving and flexuous (divaricating at maturity); hairless; about as long as the body of the lemma to much longer than the body of the lemma; entered by several veins; persistent. Lemmas hairless; scabrous; somewhat carinate; without a germination flap; 5 nerved, or 7 nerved. Palea present; relatively long; tightly clasped by the lemma; apically notched; awnless, without apical setae to with apical setae; thinner than the lemma (membranous); not indurated; 2-nerved; 2-keeled. Palea keels wingless; scabrous. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Anthers about 0.6 mm long; not penicillate; without an apically prolonged connective. Ovary apically hairy. Styles fused to free to their bases. Stigmas 2–3.

Fruit, embryo and seedling. Fruit medium sized (6–7 mm long); compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small. Endosperm containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode.

Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (thick, pitted). Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Costal short-cells predominantly paired. Costal silica bodies rounded (mostly), or crescentic (a few); not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (the groups large). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (all bundles with strong T’s to I’s). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups (in addition to strong marginal groups); abaxial-hypodermal, the groups isolated (of 1-few cells, opposite the bulliforms).

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

Distribution, phytogeography, ecology. Juan Fernandez Is. (Chile).

Species of open habitats. Rocky slopes.

References, etc. Leaf anatomical: studied by us - M. berteroniana Steud.

Illustrations. • M. berteroniana: Nicora & Rúgolo de Agrasar (1987)

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.’.