Diplacrum caricinum R.Br.

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 : 149-151

Diplacrum caricinum R.Br. , Prodr. 141 (1810)

Scleria caricina (R.Br.) Benth. , Flora Australiensis 7: 426 (1878).

Type citation: ‘(T.) B. v.s.’ Type: Queensland: Endeavour River, July–Aug. 1770, J. Banks and D. Solander; lecto BM 000833639 ( Kern 1961 a, p. 210, cited as ‘holo’; Mabberley and Moore 2022, p. 217) ; probable isolecto P 00601910 .

Dwarf herbaceous annual, glabrous, (3–) 5–35 cm high, with reddish fibrous roots. Culms tufted, more or less erect or spreading. Leaves much shorter than inflorescences; leaf blades flat, with mid-nerve prominent abaxially, glabrous, 2–5 mm wide at mid-length, margins with minute antrorsely aculeate prickle hairs towards apex, with mid-nerve and numerous finer lateral nerves prominent on abaxial surface, several nerves prominent adaxially; no ligule or contraligule (the top of the leaf sheath opposite the junction with the blade truncate, not thickened); sheaths often reddish at the base. Inflorescence much longer than the culms, with internodes ~ 8–20 mm long, composed of 3–14 remote axillary clusters of spikelets; each cluster usually with 1 or 2 basal male spikelets and an upper female spikelet. Involucral bract at each node leaf-like, shorter than the inflorescence. Male spikelets 0.7–2.0 mm long, with 1 slender, more or less hyaline glume 0.7–2.0 mm long, not indurated at maturity; stamen 1; anther 0.2–0.5 mm long, with apical appendage <0.1 mm long. Female spikelets 0.7–2.8 mm long, with 2 glumes encircling the ovary and tightly clasping the nutlet and falling with it at maturity; peduncle thickened and disclike at apical abscission zone but not enlarged and cup-like at maturity; glumes with narrow hyaline margins, 0.7–2.7 mm long including short erect (becoming incurved over nutlet at maturity) awn 0.2–0.5(–0.8) mm long, 3–9(–11)-nerved (usually only inner 3 prominent, elliptical with broad–acute to obtuse apex, with minute lateral lobes (extension of the hyaline margin on each side of the awn), green turning straw-coloured with maturity. Disc trigonous to subcircular, off-white, adhering to nutlet. Style 3-fid. Nutlet globose to broad–ovoid, circular to subtrigonous in cross-section, sparsely white-hispidulous at apex, otherwise glabrous, glossy, off-white to dark greyish, with 3 prominent paler ribs, 0.7–1.1 mm long, 0.5–0.7 mm in diameter, faintly and irregularly longitudinally rugose-ridged; somewhat tuberculate on ridges ( Fig. 3 ).

Distribution and habitat

Widespread, from India and Sri Lanka to Japan, Malesia and Australia ( Fig. 1 a , Australia and New Guinea distribution only).

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 usually taller, with broader leaf-blades and more elongated inflorescences, than the other Australian species of Diplacrum . It differs further in having persistent glumes that enclose, and fall with, the more or less globose nutlet, which is unique among these species in being minutely hispidulous at the apex. Kern (1961 b) suggested that D. reticulatum might not be distinct from D. caricinum . Diplacrum poklei is described by Chandramohan (2016) as being similar to D. caricinum , but smaller in its parts. We have not seen material of either taxon and further investigation is needed to assess their status.

Selected specimens

AUSTRALIA: NORTHERN TERRITORY: Darwin and Gulf: Kakadu National Park , 21 Apr. 1990, C. Dunlop 8542 and P.F. Munns (AD n.v., BRI n.v., CANB n.v., DNA n.v., MEL n.v., NSW 2314188 ) ; Lake Deane , 27 May 1973, P.K. Latz 3700a (DNA NT40591A, NSW 1119341; Fitzmaurice River headwaters, 12 May 1994, P.K. Latz 13847 p.p. (DNA n.v., NSW 451952 ) ; headwaters of Haywood Creek , 23 Feb. 1989, G. Leach 2146 and C. Dunlop (CANB n.v., DNA n.v., NSW 2314187 ) ; Pethericks Park , Woolaning, 1 Apr. 1990, J. Russell-Smith 8225 and E.R. Petherick (BRI n.v., DNA D0050016 n.v., NSW) ; Graveside Creek , 24 May 1987, K.L. Wilson 7392 ( NSW 196640 ) . QUEENSLAND: Cook : Yarrabah, near Cairns, 28 June 1935, S.T. Blake 9652 (BRI n.v., NSW 2314194 ) ; tributary of Escape River , 4 June 1978, J.R. Clarkson 2094 (BRI n.v., CANB 313641 , NSW 2314193 ) ; Temple Bay , 17 June 1978, J.R. Clarkson 2136 (BRI n.v., NSW 2314192 ) ; Chester River camp site, 28 July 1978, J.R. Clarkson 2424 (BRI n.v., CANB 339802 , K n.v., NSW 2314191 ) ; Browns Creek on Iron Range Road , 13 Sep. 1975, R. Coveny 7095 and P. Hind (BRI, K, L 0795372, NSW 2314195, P, US) ; Cape Tribulation , 80 miles [~ 130 km] N of Cairns, 9 June 1943, H. Flecker s.n. ( NSW 181503 ) ; just north of the Daintree River , 27 Aug. 2008, B.S. Wannan 5377 and R.L. Jago (BRI, NSW 920690 ) .

CAROLINE ISLANDS: Ponape Island , near Meilap, W coast 1–1.5 miles [~ 1.5–2.5 km] N of Palang, 18 Nov. 1978, F.R. Fosberg 58382a and M.V.C. Falanruw (NSW 2314211, US n.v.).

INDIA: Quilon , Oct. 1835, R. Wight s.n. ( NSW 2314202 ) .

INDONESIA: Sulawesi Selatan, N shore of Lake Matano E of Nuha, 30 June 1979, E.F. De Vogel 6036 (L n.v., NSW 2314212 ) .

JAPAN: Honshu , near Yozumi in Kazusa, Oct. 1955, T. Koyama s.n. ( NSW 2314196 ) .

MALAYSIA: Sabah: Mt Kalawai , 10–11 Dec. 1915, M.S. Clemens 11164 ( NSW 2314203 ) .

PAPUA NEW GUINEA: Derideri, ~ 15 km NW of Arufi, Morehead Road, 23 Sep. 1990, S.W.L. Jacobs 5971 and B.J. Conn (GENT, LAE, NSW 253616 ); garden at Sigabaduru village , mainland PNG, W of Daru, 3 June 1999, A.A. Mitchell 5823 and V. Gei (CANB n.v., LAE n.v., MBA n.v., NSW 1055489 ); Tiaura, Saru River track, 5 miles [~ 8 km] SE of Garaian, Lae Subdistrict , Morobe District, 18 July 1970, H. Streimann and A. Kairo NGF 47956 (A n.v., BO n.v., BRI n.v., CANB 217027 , K n.v., L 0795384 (image seen), LAE n.v., NSW 2314210, SING n.v.) .

PHILIPPINES: Luzon : Paracale, Camarines Province, Nov.–Dec. 1918, M. Ramos and Q. Edaño BS 33507 ( NSW 2314204 ) .

Figures

Fig. 3. Diplacrum caricinum. (a) Habit. (b) Inflorescence. (c) Cluster of spikelets. (d, e) Nutlets (three upper-most nutlets surrounded by persistent glumes). Vouchers: (a) J. Russell-Smith 8225 and E.R. Petherick (NSW); (b–e) P.K. Latz 3700a (NSW). Scale bars: 1 cm (a, b), 1 mm (c), 0.5 mm (d, e). 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.