Diplacrum latzii K.L.Wilson et R.L.Barrett, 2023

Wilson, Karen L. & Barrett, Russell L., 2023, Revision of the tropical genus Diplacrum (Cyperaceae: Bisboeckelereae) in Australia, Australian Systematic Botany 36 (2), pp. 143-156 : 151

Diplacrum latzii K.L.Wilson et R.L.Barrett , sp. nov.

Type: Northern Territory: 17 miles [~ 27 km] N Wilton River Crossing , 15 June 1972, P.K. Latz 2756a; holo NSW 1119274; iso BRI, DNA D0006219 n.v., K n.v., L n.v., NT 35325 .

Scleria sp. Wilton River (P.K.Latz 2756A) P.S. Short, D.E. Albrecht, I.D.Cowie, D.L.Lewis & B.M.Stuckey (eds), Checkl. vasc. pl. N. Terr. 28 (2011)

Diagnosis

Nutlets narrow–ellipsoid to narrow–ovoid, obscurely trigonous in cross-section, obscurely 3-ribbed longitudinally, glabrous, smooth; female glumes 0.8–1.5 mm long (including slightly excurved awn 0.2–0.5 mm long, usually slightly shorter than the body of the glume); leaves shorter than inflorescences.

Dwarf herbaceous annual, glabrous, plants 1.5–8 cm high, with reddish fibrous roots. Culms tufted, more or less erect. Leaves shorter than to equalling inflorescences; leaf blades flat, glabrous, margins with minute antrorsely aculeate prickle hairs towards apex, 0.7–1.5 mm wide at mid-length, with 3–5 nerves prominent on adaxial surface, 3–7 nerves prominent on abaxial surface; no ligule or contraligule (top of leaf sheath opposite the junction with the blade truncate, not thickened); sheaths often reddish at the base. Inflorescence approximately the same length as to longer than the culms, 1–2 cm long, internodes 2–8 mm long, composed of 2–5 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, shorter than inflorescence, scabrous towards apex. Male spikelets ~ 0.5 mm long, with 1 slender more or less hyaline glume ~ 0.5 mm long, becoming chartaceous and dark reddish-brown with age; stamen 1; anther ~ 0.3 mm long, with apical appendage <0.1 mm long. Female spikelets 1.3–2.0 mm long, with 2 glumes encircling the ovary but not tightly clasping the nutlet nor falling with it; glumes narrow–elliptical, with acute to obtuse apex, green drying to straw-coloured with minute red dots, with narrow to broad hyaline margins, 0.8–1.5 mm long (including slightly excurved awn 0.2–0.5 mm long, usually slightly shorter than the body of the glume), 3–5-nerved with only mid-nerve or 3 nerves prominent; peduncle often somewhat thickened at apex at maturity (less obvious than in D. pygmaeum ). Disc triquetrous, white, adhering to nutlet. Style 3-fid. Nutlet narrow–ellipsoid to narrow–ovoid, obscurely trigonous in cross-section, obscurely 3-ribbed longitudinally, glabrous, smooth, glossy, mid- to dark yellowish-brown to purplish, ~ 0.4 mm long, ~ 0.3 mm in diameter. ( Fig. 4 )

Distribution and habitat

Tropical Northern Territory and Western Australia ( Fig. 1 c ); may also occur in northern Queensland but no specimens have been seen. Commonly grows with D. blakei , D. caricinum , D. pygmaeum and other annual sedges on the margins of wet areas.

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).

Etymology

Named after Dr Peter Kenneth Latz (1941‒), who has contributed so much to our knowledge of tropical and central Australian sedges and many other plant groups.

Notes

This species is similar in habit to D. blakei and D. pygmaeum , differing from them most obviously in the smooth, narrow–ellipsoid to narrow–ovoid nutlet, broadly 3-angled but lacking prominent ribs. This species appears to be similar to D. exiguuum , based on the description of that species by Kern (1962 [as Scleria pygmaea ]), particularly in the smooth, 3-angled nutlet, but D. exigua is described as having female spikelets with glumes only mucronulate whereas those of D. latzii have an elongated awn.

Specimens examined

WESTERN AUSTRALIA: 24 km NW of Drysdale River crossing, 6 km W of Gibb River – Kalumburu Mission road, 30 May 1976, A.C. Beauglehole 51691B (DNA A0067966, MEL n.v., NT 51120, PERTH 6217079 ) . NORTHERN TERRITORY: Darwin and Gulf: about S of Brocks Creek, between (near junction of) Hayes Creek and Douglas River , 29 June 1946, S.T. Blake 16227 (BRI-AQ172758, NSW 1119272 ) ; O.T. Station, 5 May 1947, S.T. Blake 17647A ( BRI-AQ173036 ) ; Kakadu National Park , site 98, 19 km NNW of Twin Falls, 3 June 1980, L.A. Craven 6297 ( CANB 318175 ) ; 17 miles [~ 27 km] N Wilton River Crossing, 15 June 1972, P.K. Latz 2755 p.p. (DNA, NSW 1119245 ) ; Lake Deane , 26 May 1973, P.K. Latz 3701 (DNA NT40592, NSW 1119273 ) ; Kakadu National Park, Buba Billabong , 4 May 1995, N.M. Smith 3706 p.p. (DNA D0157362 n.v., NSW 623105 ) .

Figures

Fig. 4. Diplacrum latzii. (a, b) Habit. (c) Inflorescence. (d) Cluster of spikelets. (e, f) Nutlets. Vouchers: (a) S.T. Blake 16227 (NSW); (b–d) P.K. Latz 2756a (NSW); (e, f) P.K. Latz 3701 (NSW). Scale bars: 1 cm (a–c), 2 mm (d), 1 mm (e), 0.5 mm (f). Photos: R.L. Barrett.

Fig. 1. Distribution of Diplacrum species in Australia and Papua New Guinea based on data from the Australasian Virtual Herbarium (see https://avh.ala.org.au/, accessed June 2022). (a) D. caricinum. (b) D. blakei. (c) D. latzii. (d) D. pygmaeum.