Platychorda B.G.Briggs & L.A.S.Johnson

Reference
Telopea 7:359-360 (1998)
Name Status
Current

Scientific Description

Family Restionaceae.

Habit and leaf form. Herbs (the base pubescent in the axils of glabrous cataphylls); evergreen. Switch-plants; with the principal photosynthesizing function transferred to stems (culms). Leaves well developed, or much reduced (the blade being much reduced or absent). Perennial. Young stems broad, somewhat flattened (erect, striate, without scabrid edges); not breaking easily at the nodes. Stem internodes hollow. Rhizomatous. Leaves alternate; distichous, or spiral; leathery, or membranous; sessile; sheathing (and more or less reduced to the sheaths). Leaf sheaths with free margins (persistent, appressed, scarious or membranous with gradually tapering auriculate apices). Leaves simple; with a persistent basal meristem, and basipetal development. Vegetative anatomy. Plants with silica bodies. Leaf anatomy. Leaf blade epidermis conspicuously differentiated into ‘long’ and ‘short’ cells, or without differentiation into ‘long’ and ‘short’ cells. Guard-cells not ‘grass type’, or ‘grass type’. Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Unisexual flowers present. Plants dioecious. Female flowers with staminodes, or without staminodes. Male flowers with pistillodes, or without pistillodes. Floral nectaries absent (nectaries absent). Anemophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in ‘spikelets’. Inflorescences scapiflorous, or not scapiflorous; terminal; male and female inflorescences similar, spikelets at several or many nodes of slender branches, the branches singly or in clusters at several upper nodes; spikelets with many sterile lower glumes; glumes blunt or acute. Flowers bracteate; bracteolate, or ebracteolate; cyclic. Perigone tube absent. Perianth of ‘tepals’; members 6 (2 outer tepals keeled); 2 -whorled; isomerous; sepaloid. Fertile stamens present, or absent (when female). Androecium 3. Androecial members free of the perianth; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 3; remaining included; isomerous with the perianth; oppositiperianthial (opposite the inner perianth members). Anthers dorsifixed; versatile, or non-versatile; dehiscing via longitudinal slits; introrse, or latrorse; bisporangiate, or tetrasporangiate; appendaged, or unappendaged. Pollen shed as single grains. Fertile gynoecium present, or absent (male flowers). Gynoecium 3 carpelled. The pistil 3 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary plurilocular; 3 locular; sessile to stipitate. Gynoecium stylate. Styles 3; partially joined. Placentation axile to apical. Ovules 1 per locule; funicled, or sessile; pendulous; non-arillate; orthotropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 3 seeded. Seeds copiously endospermic. Embryo weakly differentiated. Testa with irregular pattern of subangular or slightly lobed, flat or slightly convex, isodiametric cells. Seedling. Hypocotyl internode absent. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling cataphylls absent. First leaf centric. Primary root ephemeral.

Additional characters Stems glabrous; simple (below the inflorescence); not dimorphic. Male spikelets several-flowered (erect or somewhat pendulous). Female spikelets several-flowered (erect). Caespitose.

H.R. Coleman, 8 September 2016

Taxonomic Literature

  • Wheeler, Judy; Marchant, Neville; Lewington, Margaret; Graham, Lorraine (2002). Flora of the south west, Bunbury, Augusta, Denmark. Volume 1, introduction, keys, ferns to monocotyledons. Australian Biological Resources Study. Canberra.
  • Briggs, Barbara G.; Johnson, L. A. S. (2001). New species of Harperia, Loxocarya, Onychosepalum, Platychorda and Tremulina (Restionaceae) in Western Australia.
  • Briggs, Barbara G.; Johnson, L. A. S. (1998). New genera and species of Australian Restionaceae (Poales).