Diplacrum pygmaeum Boeckeler
Creators: name: Wilson, Karen L.
name: Barrett, Russell L.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Poales
Cyperaceae
Diplacrum
Diplacrum pygmaeum

description: Diplacrum pygmaeum (R.Br.) Nees ex Boeckeler, Linnaea 38(4): 434 (1874)
Scleria pygmaea R.Br., Prodr. 240 (1810). Hypoporum pygmaeum (R.Br.) Nees, Linnaea 9: 303 (1834).
Type citation: ‘(T.) B. v.s.’ Type: Queensland: Endeavour River, July–Aug. 1770, J. Banks and D. Solander (lecto BM000900962; probable isolecto BM 000900963, BRI-AQ0341623, NSW 268828, P 00601916, P 00601917; fide K.L. Wilson in D.J. Mabberley and D.T. Moore, Regnum Veg. 160: 232 (2002)).
Sphaeropus pygmaeus Boeckeler, Flora 56: 89 (1873).
Type citation: ‘ Fr. Schulz pl. Austral. no. 260 – (Herb. Berolin.) … Nova Holland., Adelaide.’ Type: Northern Territory: Port Darwin, F. Schultz 260; holo B?, n.v.; iso MEL 2297608.
Dwarf herbaceous annual, glabrous, 2–15 cm high, with reddish fibrous roots. Culms tufted, more or less erect or spreading. Leaves shorter than inflorescences; leaf blades flat, midrib prominent abaxially, glabrous, margins with minute antrorsely aculeate prickle hairs towards apex, 1.0– 2.5 mm wide at mid-length, with mid-nerve and 2 or more lateral nerves prominent on adaxial surface, mid-nerve prominent on abaxial surface; no ligule or expanded contraligule (the top of the leaf sheath opposite the junction with the blade truncate, not thickened); sheaths reddish at the base. Inflorescence much longer than the culms, with internodes 2–20 mm long, composed of 2–6 remote axillary clusters of spikelets; each cluster with 0–2 basal male spikelets and an upper female spikelet. Involucral bract at each node leaf-like, usually much longer than inflorescence. Male spikelets 1.0– 1.3 mm long, with 1 slender, more or less hyaline glume 1.0– 1.3 mm long, not indurated at maturity; stamen 1; anther ~ 0.2 mm long, with apical appendage <0.1 mm long. Female spikelets 2.0– 3.2 mm long, with 2 glumes encircling the ovary but not tightly clasping the nutlet nor falling with it; peduncle thickened at apex and cup-like at maturity; glumes with narrow hyaline margins, 2.2–3.0 mm long, including somewhat excurved awn 0.8–1.2 mm long, nearly as long as the body of the glume, 3-nerved (usually only mid-nerve prominent, narrow–elliptical with broad–acute apex, green turning straw-coloured with maturity, margins hyaline. Disc trigonous to circular, dark grey to blackish, with 6 off-white fine lines radiating from the centre, adhering to the nut. Style 3-fid. Nutlet globose, circular to subtrigonous in cross-section, glabrous, glossy, off-white maturing to dark purplish to blackish, slightly paler at apex, with 3 slightly paler longitudinal ribs and 3 paler swollen lobes at the base (adjacent to the disc) with a narrow yellowish-brown line between the lobes, 0.6–0.7 mm long, 0.5–0.6 mm in diameter, minutely colliculate or papillose, often more or less rugose when young (Fig. 5).
Distribution and habitat
Widespread in tropical Australia, from the West Kimberley east to around Rockingham Bay in Queensland (Fig. 1 d). Grows in seasonally damp sands and loams, on the margins of swamps with a wide range of herbaceous species.
Conservation status
Widespread, including in national parks, so not considered at risk. We suggest a status of ‘Least Concern’ (International Union for Conservation of Nature 2019).
Notes
This species is similar in habit to D. blakei and D. latzii, differing most obviously in the more or less globose nutlet and the longer awn on the female glumes. D. caricinum also has a globose nutlet, but it differs from D. pygmaeum in the nutlet falling tightly clasped by the two glumes and in having a generally taller habit, with an elongated inflorescence.
Specimens examined
WESTERN AUSTRALIA: Mainland 8.3 km SE of Gertrude Cove on Kiska Island, N of Roe River mouth, West Kimberley, 23 Apr. 2008, M.D. Barrett and R.L. Barrett MDB 1988 (PERTH 9339256); 18.3 km WNW of Munja Airstrip, Harding Range, West Kimberley, 22 Apr. 2008, M.D. Barrett and R.L. Barrett MDB1923 (PERTH 9339132); ‘ Skull Creek’ camp and trap site, Doongan Station, 24 Apr. 2008, R.L. Barrett RLB4671 (PERTH); beside King Edward River crossing on old Mitchell River Station Road, Doongan Station, North Kimberley, 28 Apr. 2007, R.L. Barrett RLB5823 (PERTH); Youwanjela pavement 1, 26.7 km E of Kings Cascades; 12.4 km NNE of junction of Youwanjela Creek and Prince Regent River, Prince Regent Nature Reserve, 25 Jan 2007, R.L. Barrett and M.D. Barrett RLB7264 (PERTH 8824258); DMR 008 site, 7 km SE of King Edward River on old Mitchell River Road, 30.7 km NW of Doongan Homestead, 18 May 2011, R.L. Barrett RLB7264 (PERTH 9338012); 1.5 km W of Lennard River Gorge turn-off, Gibb River Road, 24 July 1974, G.W. Carr 4101 and A.C. Beauglehole 47879 (DNA NT50726, PERTH 1299034). NORTHERN TERRITORY: Darwin and Gulf: Western Arnhem Land, ~ 94 km ESE of Jabiru, 20 Mar. 2000, I.D. Cowie 8680 (DNA D01411676 n.v., NSW 537187); ~ 10 km NE ‘ Mudginbarry’ [sic; Mudginberri] on Oenpelli road, 1 June 1974, S.W.L. Jacobs 1806 (CANB 257416, K, NSW 1119254, NT, P, READING); Mt Brockman Outlier, 15 km SE of Jabiru, 20 Apr. 1989, R.W. Johnson 4765 (BRI n.v., DNA n.v., NSW 470746); Lake Deane, 26 May 1973, P.K. Latz 3700B (NT 40591, p.p.); Cox River Station, 4 July 1977, P.K. Latz 7225 (DNA, NSW 2314168); Fish River block, 15 Apr. 2010, D.L. Lewis 1330 (DNA n.v., LD, NSW 928734); 4.2 km towards Ramingining from Central Arnhem Road, 22 July 1999, P.S. Short 4989 and R.K. Harwood (DNA, NSW 675668); South Bay, Bickerton Island, in the Gulf of Carpentaria, 19 June 1948, R.L. Specht 624 (CANB 29135, MEL 2204177, NSW 1119253, PERTH 2331985); track to Winmurra Billabong from Oenpelli Road, 6 May 1983, K.L. Wilson 5163 (DNA, H, K, NE, NSW 840767, P); Barramundie Gorge, 20 May 1987, K.L. Wilson 7305 (NSW 206397); Graveside Creek, 24 May 1987, K.L. Wilson 7392a (NSW 1119295); Red Lily Lagoon, Kapalga, 28 May 1987, K.L.Wilson 7457 (NSW 196723); 19 km N of Arnhem Highway on track to Four Mile Hole, 30 May 1987, K.L. Wilson 7477 (NSW 196743). QUEENSLAND: Cook: near Cooktown, 17 May 1970, S.T. Blake 23354 (BRI, NSW 1119247); east bank of Little Laura River, S of Laura, 20 May 1975, N. Byrnes 3425 (BRI, NSW 225743); Codroy Creek 5.3 km N of Hann River on Laura to Musgrave road, 1 June 1989, J.R. Clarkson 8037 and V.J. Neldner (BRI-AQ591471 n.v., K n.v., NSW 2314174); 37 km SSE of Aurukun, ~ 12 km E of the Archer River, 28 May 1982, J.R. Clarkson 4387B (BRI-AQ0367052 n.v., K n.v., NSW 2314173); Browns Creek on Iron Range Road (174 km [~ 108 miles] N of Coen by road, 13 Sep. 1975, R.G. Coveny 7095b and P.D. Hind (NSW 1119248); Bulleringa National Park, 80 km NW of Mount Surprise, Donkey Spring Creek, 23 Apr. 1998, P.I. Forster PIF22528 and R. Booth (BRI n.v., NSW 461971); ~ 5 km N of Ayton, Cooktown road, 22 May 1976, S.W.L. Jacobs 2734 and A.N. Rodd (BRI, NSW 1119252); W of Petford, 23 May 2009, B.S. Wannan 5660 and J. Beasley (BRI, NSW 823068); Dulhunty River crossing, 18 km SW of Heathlands base (by road), 6 Mar. 1992, K.L. Wilson 8253 and P. Sharpe (DNA, MBA, NSW 339173). North Kennedy: Rockingham Bay, J. Dallachy s.n. (NSW 1119246 ex MEL).
description: Published as part of Wilson, Karen L. & Barrett, Russell L., 2023, Revision of the tropical genus Diplacrum (Cyperaceae: Bisboeckelereae) in Australia, pp. 143-156 in Australian Systematic Botany 36 (2) on pages 151-154, DOI: 10.1071/SB22028, http://zenodo.org/record/10904311