Oplismenus P.Beauv.
Type species: O. africanus P.Beauv.
Perennials or annuals, ± weak, trailing, often carpet-forming, decumbent and rooting at lower nodes with slender ascending leafy culms. Leaf-sheath < internodes, keeled above, often with minute cross-veinlets, open; margins often hair-fringed, overlapping. Ligule ciliate. Leaf-blade thin, flat, ovate to lanceolate, usually variously pubescent; margins finely scabrid. Inflorescence a racemose panicle with spikelets solitary, or in pairs or racemelets, falling entire at maturity; rachis, branches and pedicels slender, angular. Spikelets 2-flowered; lower floret ♂ or Ø, upper floret ⚥. Glumes ± equal, < florets, membranous, 3-7-nerved, ± keeled above, both, or at least the lower, apically awned. Lower floret: lemma similar to glumes in texture, 5-9-nerved, mucronate to shortly awned; palea = lemma, or reduced, or 0. Upper floret: lemma chartaceous to subcoriaceous, oblong, glabrous, margins enfolding palea, awnless; palea = lemma; lodicules 2, broadly cuneate; stamens 3; ovary apex glabrous, styles terminal to subterminal, free to base; caryopsis tightly enclosed by anthoecium, embryo large, hilum linear, variable in length. Fig. 22.
c. 7 tropical to subtropical spp. extending into warm temperate regions in both Hemispheres; usually found on shaded forest floors. The 1 sp. indigenous to N.Z. is also widespread in the tropics, South Pacific and Australia.
Oplismenus was reviewed by Davey, J. C. and Clayton, W. D. Kew Bull. 33: 147-157 (1978); and monographed by Scholz, U. Phan. Monogr. 13: 1-213 (1981).
Cheeseman (1925 op. cit.) referred N.Z. plants to O. undulatifolius P.Beauv., but this is a conspicuously long-awned sp. with spikelets clustered in fascicles, occurring in warm temperate regions of the Northern Hemisphere and extending southwards only into Africa and India. Under Davey and Clayton's treatment (1978 op. cit.) N.Z. mainland plants would fall into O. hirtellus (L.) P.Beauv.; their "hirtellus group" comprised O. hirtellus, O. aemulus, and O. imbecillis. Scholz (1981, op. cit.) referred N.Z. material to O. aemulus var. flaccidus (R.Br.) Domin and treated Kermadec Is plants as O. hirtellus subsp. imbecillis (R.Br.) U.Scholz forma imbecillis whereas Fosberg, F. R. and Sachet, M. H. Micronesica 18: 45-102 (1982) preferred varietal rank for the latter as O. hirtellus var. imbecillis (R.Br.) Fosberg et Sachet.
Sykes, W. R. and West, C. J. N.Z. J. Bot. 34: 447-462 (1996) recognised two taxa on the Kermadec Is, O. hirtellus subsp. hirtellus and O. hirtellus subsp. imbecillis; both subspecies may also be present in northern North Id, but only subsp. imbecillis occurs further south. Their treatment is followed here.
