Dielsia Gilg
Bot.Jahrb.Syst. 35:88, fig. 6 A-L. (1904)

Name Status: Current
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Scientific Description
H.R. Coleman, Thursday 8 September 2016

Family Restionaceae.

Habit and leaf form. Herbs; 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 cylindrical (striate); not breaking easily at the nodes. Stem internodes solid, or hollow. Rhizomatous (rhizomes stout, villous). Helophytic. 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). 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 solitary, erect, elongated, cylindrical; glumes scarious-membranous. Flowers bracteate; bracteolate, or ebracteolate; cyclic. Perigone tube absent. Perianth of ‘tepals’; members 6 (outer 2 keeled, the keel densely red-brown pubescent); 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; 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 2 carpelled, or 3 carpelled. The pistil 2 celled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary plurilocular; 2 locular; sessile to stipitate. Gynoecium stylate. Styles 2; free, or 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 1–3 seeded. Seeds copiously endospermic. Embryo weakly differentiated. Testa smooth (with longitudinal lines of transversely elongated rectangular 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 Perianth of male flowers of ‘tepals’; 6. Perianth of female flowers of ‘tepals’; 6. Stems much branched (upper branches often flexuose and sometimes forming dense trailing masses); not dimorphic. Male spikelets many-flowered. Female spikelets many-flowered. Not caespitose. Female spikelets simple. Spikelets more than 10 mm long.

Taxonomic Literature

  • Briggs, Barbara G.; Johnson, L. A. S.; National Herbarium of New South Wales (1998). New combinations arising from a new classification of non-African Restionaceae.