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Castrate Carpetgrass (Arthraxon castratus)

Description

Andropogon castratus Griffith, Not. Pl. Asiat. 3: 89. 1851; A. pilipes Backer; A. rudis Nees ex Steudel; Arthraxon haina-nensis Keng & S. L. Chen; A. rudis (Nees ex Steudel) Hochstetter. Perennial. Culms straggling, decumbent, rooting from lower nodes, 60-200 cm long, culm apex pubescent. Leaf sheaths glabrous to densely papillose-hispid; leaf blades lanceolate, 3-11 cm - 7-15 mm, glabrous or sparsely appressed-hispid, base cordate, margins pectinate-setose, apex acuminate; ligule 1-2 mm. Racemes 2-5, 3-7 cm, brownish green or purplish brown, raceme bases slenderly terete, pubescent; rachis internodes 1/3-4/5 length of sessile spikelets, softly pilose, hairs 0.4-1.5 mm. Sessile spikelet 4-8 mm; lower glume broadly lanceolate, leathery, weakly convex, not laterally keeled, margins flat, back asperulous, 7-9-veined, tuberculate-spinulose above middle especially near margins, spicules longer toward apex; upper glume longer than lower glume, broadly leathery, hyaline margins 0.1-0.2 mm, spicules present along upper midline; lemma margins ciliate; upper lemma 2-toothed, teeth ca. 0.4 mm; awn 10-14 mm; palea lanceolate, 1/2 length of lemma. Anthers 3, 2-3.8 mm. Pedicelled spikelet absent; pedicel subulate, 1-3 mm, pilose. Fl. and fr. autumn-winter. 2n = 18, 36. Dry mountain slopes. Hainan [India, Indonesia, Myanmar, Sri Lanka, Thailand, Vietnam; Australia (Queensland)]. Arthraxon castratus has a distinctive, narrowly elongate, pubescent base to each raceme, and the pubescence is carried down onto the upper part of the culm. The unusually broad, leathery upper glume also imparts a characteristic, broad side view to the spikelets.

Taxonomic tree

  • Domain: Eukarya

    • Kingdom: Plantae

      • Phylum: Magnoliophyta

        • Class: Liliopsida

          • Order: Poales

            • Family: Poaceae

              • Genus: Arthraxon