13.17   DUPONTIA R. Br.

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Jacques Cayouette
Stephen J. Darbyshire

Plants perennial; rhizomatous. Culms 5-80 cm. Sheaths closed for 1/2-2/3 of their length, glabrous; auricles absent; ligules membranous, glabrous, truncate; blades flat or folded, usually glabrous, sometimes scabrous or shortly pubescent adaxially. Inflorescences panicles, diffuse to dense and spikelike, with few spikelets; branches smooth, stiff, erect to reflexed, secondary branches usually appressed. Spikelets pedicellate, slightly laterally compressed; florets 1-4(5), distal florets sterile; rachillas prolonged beyond the uppermost floret or terminating in a vestigial floret, glabrous; disarticulation above the glumes and beneath the fertile florets. Glumes subequal, equaling or usually exceeding the distal florets, ovate and obtuse to lanceolate-attenuate, membranous, glabrous, 1-3-veined; calluses short, blunt, with a ring of stiff hairs, hairs to about 1 mm; lemmas ovate to ovate-lanceolate, membranous to coriaceous, glabrous or pubescent, with 3(5) fine veins, apices acute to acuminate, midveins sometimes excurrent as a mucro or awn to 1(2.2) mm; paleas shorter than the lemmas, glabrous, sometimes scabrous on the veins; lodicules 2, membranous, glabrous; anthers 3; ovaries glabrous. Caryopses falling free of the lemma and palea; hila 1/6-1/3 the length of the caryopses, ovate. x = not clear, 7 or 11. Named after the early nineteenth century French botanist J.D. Dupont.

Dupontia is a monotypic genus of arctic and subarctic wetlands, found throughout the holarctic region except in Scandinavia. Hybrids with Arctophila are referred to ×Arctodupontia; hybrids with Poa eminens are referred to ×Dupoa.

SELECTED REFERENCES Brysting, A.K., S.G. Aiken, L.P. Lefkovitch, and R.L. Boles. 2003. Dupontia (Poaceae) in North America. Canad. J. Bot. 81:769-779; Brysting, A.K., M.F. Fay, I.J. Leitch, and S.G. Aiken. 2004. One or more species in the arctic grass genus Dupontia? A contribution to the Panarctic Flora project. Taxon 53:365-382; Jurtsev, B.A. 1995. Dupontia. Pp. 224-229 in J.G. Packer (ed., English edition). Flora of the Russian Arctic, vol. 1, trans. G.C.D. Griffiths. University of Alberta Press, Edmonton, Alberta, Canada [English translation of A.I. Tolmachev, ed. (1964). Arkticheskaya Flora SSSR, vol. 2. Nauka, Leningrad, Russia].

1.   Dupontia fisheri R. Br.
Fisher's Tundragrass, Dupontie de Fisher

Rhizomes 1-3 mm thick, nodes with whorls of roots. Culms 5-80 cm, erect, glabrous. Ligules of lower leaves 0.4-3 mm; ligules of flag leaves 1-4(5.5) mm, usually lacerate; blades 1-13 cm long, 1-4 mm wide. Panicles 2.5-18 cm long, 1-6 cm wide. Spikelets 4-8.5(9) mm; rachilla internodes 1-1.5 mm. Glumes 4-8.5(9) mm; lemmas 3-6.5 mm; paleas 2.8-6 mm; anthers 1.5-3.5 mm. Caryopses 1.5-3 mm. 2n = 42, 44, 66, 84, 88, 132.

Dupontia fisheri grows in wet meadows, wet tundra, marshes, and along streams and the edges of lagoons, ponds, and lake shores, in sand, silt, clay, and moss, rarely in bogs. It is sometimes dominant, or co-dominant, with Alopecurus borealis.

Two subspecies are sometimes recognized in North America. Dupontia fisheri R. Br. subsp. fisheri supposedly differs from subsp. psilosantha (Rupr.) Hultén in being less than 40 cm tall, having erect panicle branches, 2-4 florets per spikelet, pubescent, obtuse lemmas, and 2n = 84, 88, or 132. Dupontia fisheri subsp. psilosantha is taller, has reflexed panicle branches, 1-2 florets per spikelet, more or less glabrous, acute lemmas, and 2n = 42 or 44. Plants referable to subsp. psilosantha are restricted to coastal marshes, rarely penetrating inland along riparian habitats, from James Bay to the lower arctic archipelago. Plants referable to subsp. fisheri are less halophytic and more northerly in their distribution, being found in a variety of inland marshes and wet tundra habitats from northern Alaska to Ellesmere Island. Intermediates are readily found (e.g., hexaploid, 2n = 66 hybrids from Alaska) and the correlations among chromosome number, morphology, ecology, and distribution are relatively weak in North America and Greenland. For these reasons, no subspecific taxa are recognized in this treatment.