Megathyrsus (Pilg.) Simon & Jacobs, Austrobaileya 6: 572. 2003.

Description by Jacobs, S.W.L., Whalley, R.D.B. & Wheeler, D.J.B., Taxon concept: Grasses of New South Wales, Fourth Edition (2008).

Caespitose perennials with short, thick rhizomes with erect culms. Nodes pubescent or glabrous. Sheaths glabrous or pubescent, sometimes with papillose-based hairs, margins sometimes ciliate; ligule of hairs; blade flat, erect or ascending, glabrous or with hairs, sometimes with appressed papillose-based hairs, margins sometimes ciliate basally. Inflorescence an open panicle with smooth or scabrous rachis, branches single or whorled at the lowest nodes, lower axils with a tuft of hairs, base, upper axils glabrous. Spikelets solitary, paired or in triplets, usually appressed to the branch axes. Glumes appresed to the florets, rachilla between the glumes not pronounced; lower shorter than the spikelet, 1–3-veined, obtuse or truncate, glabrous; upper glume subequal to the upper floret, 5-veined, glabrous. Sterile lower lemma staminate, subequal to the upper floret, glabrous, 5-veined, without cross venation, acute, muticous or mucronate. Upper fertile lemma ellipsoid, pale, glabrous, transversely rugose, apices acute or mucronulate.

2 species

Megathyrsus maximus (Jacq.) B.K. Simon & W.L. Jacobs, Austrobaileya 6: 572. 2003; Panicum maximum Jacq., Icon. Pl. Rar. 1:2, t. 13. 1781; Bor, Grasses Burma, Ceyl. Ind. Pak. 327. 1960; Sharma & Khosla, Grasses Punj. and Chandigarh 144. 1989; Fl. China @ eFloras.org 22: 506; Fl. Pak. @ eFloras.org p. 164; P. maximum var. hirsutissimum (Steud.) Oliver, Trans. Linn. Soc. 29: 171. 1875; P. maximum subsp. pubescens M.Sharma, J. Econ. Taxon. Bot. 7: 106. 1985; P. hirsutissimum Steud., Syn. Pl. Glum. 1: 71. 1854; Urochloa maxima (Jacq.) Webster, Austral. Paniceae: 241. 1987.

Perennial, rhizomatous, rhizome stout, densely tufted. Culms erect or ascending, 1-2 m tall, nodes glabrous or bearded. Leaves basal and cauline; leaf blades linear to narrowly lanceolate, flat, 20-50 cm x 0.5-2 cm, narrowed at base, base rounded, glabrous, margins scabrid, apex acuminate; leaf sheaths striate, glabrous or pubescent with tubercle-based hairs; ligule ca. 2 mm long, membranous, fimbriate. Inflorescence an ovate, oblong or pyramidal, open or contracted panicle 10-45 cm long, decompound, branches to 18 cm long, spreading, lowest arranged in a whorl, upper alternate. Spikelets elliptic-oblong, awnless, ca. 3 mm x 1 mm, symmetrical, dorsally compressed, densely pubescent, often tinged purple, obtuse or acute, disarticulating below glumes, 2-flowered. Pedicels scabrid. Glumes membranous, densely hairy, unequal, tinged purple; lower glume short, ca. 1 mm x 1 mm, 1/4 to 1/3 the length of the spikelet, orbicular, 1-3-nerved; upper glume ovate-oblong, ca. 3 mm x 1 mm, as long as the spikelet, 5-7-nerved, obtuse. Lower floret: Barren, its lemma (lower lemma) herbaceous, nearly equal and similar to upper glume, ca 2.5 mm x 1 mm; palea (lower palea) slightly shorter and narrower than lower lemma, ca. 2 mm x 0.5 mm, hyaline, 2-keeled. Upper floret: Bisexual. Its lemma (upper lemma) slightly shorter than lower lemma, ca. 2.25 mm x 1.75 mm, +/- ovate, coriaceous, transversely rugose, 2-keeled, keels scabrid, margin clasping only the margins of palea. Upper palea slightly shorter than upper palea, ca. 2 mm x 1.25 mm long, coriaceous, +/- transversely rugose, 2-keeled, acute or obtuse. Stamens 3; filaments delicate. Stigmas 2, plumose. Caryopsis +/- ovate, ca. 1.5 mm long, dorsally compressed.

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