Grass Genera of the World

L. Watson 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; an unfringed membrane; not truncate (elongated, laciniate); 5–10 mm long.

Reproductive organization. Plants bisexual, 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. Spikelets without proximal incomplete florets.

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 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).

Taxonomy. Pooideae; Poodae; Poeae.

Distribution, ecology, phytogeography. 2 species; Juan Fernandez Is. (Chile). Species of open habitats. Rocky slopes.

Neotropical. Fernandezian.

References, etc. Leaf anatomical: this project.


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).

Index