Family: Poaceae |
John W. Thieret† Plants annual or perennial; scrambling. Culms 0.5-2 m, ascending to decumbent, often rooting at the nodes, branched. Leaves not aromatic; sheaths open, at least the outer margins pubescent, usually with papillose-based hairs; ligules membranous, fimbriate or ciliate; blades ovate to ovate-lanceolate. Inflorescences terminal and axillary, panicles of subdigitate, often flabellate, clusters of rames; rame internodes not sulcate; disarticulation in the rames, beneath the sessile spikelets. Spikelets in heteromorphic sessile-pedicellate pairs or appearing solitary and sessile, pedicels greatly reduced and lacking spikelets. Sessile spikelets bisexual, with 2 florets; calluses absent or blunt; glumes equal or subequal; lower florets sterile, reduced to an unawned lemma; upper florets bisexual, awned (rarely unawned); anthers 2 or 3. Pedicels 0.2-3 mm, not thickened, not fused to the rame axes. Pedicellate spikelets absent or rudimentary. x = 9, 10. Name from the Greek arthron, segment, and axon, axis, referring to the jointed inflorescence axes. SELECTED REFERENCE Welzen, P.C. van. 1981. A taxonomic revision of Arthraxon Beauv. (Gramineae). Blumea 27:255-300. T.A. Cope (1995) Arthraxon. Flora of Somalia 4:263-264 Plants annual or perennial, with slender, often trailing, stems. Leave: ligules membranous; blades wide, usually lanceolate, bases cordate and amplexicaul. Inflorescences terminal and axillary, not leafy, subdigitate clusters of spikelike branches, branch internodes filiform to linear. Sessile spikelets dorsally or laterally compressed; calluses truncate,; lower glumes membranous to coriaceous, backs usually usually rounded, with or withour lateral keels, often scabrous or muricate; lower florets of reduced to hyaline lemmas; upper florets with hyaline subentire lemmas, backs bearing a glabrous geniculate awn from the lower half. Pedicellate spikelets variable, from as large as the sessile spikelets to highly reduced. Arthraxon is a pan tropical genus. It is here treated as a genus of 23 species, in accordance with the recommendation of Plants of the World Online (POWO), but van Welzen (see references) reduced the number to 7.One species, Arthraxon prionodes, is known from Somaliland. van Welzen included it in Arthraxon lanceolatus, a species that Cope states is confined to southern India and differs in having sessile spikelets with lower glumes of the sessile spikelets that are more or less flat and strongly veined. The Flora of Somalia did not report any species from Somalia. POWO (2022) Arthaxon Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/ Retrieved 16 August 2022. Welzen, P.C. van (1981) A taxonomic revision of Arthraxon Beauv. (Gramineae). Blumea 27:255-300. Global distribution of Arthraxon. Note: GBIF records include introduced and cultivated plants. Consequently, the distribution shown often differs from statements about a taxon's native distribution. |