Digitaria longiflora (Retz.) Pers. (1805: 85)

Boonsuk, Boonchuang, Chantaranothai, Pranom & Hodkinson Abstract, Trevor R., 2016, A taxonomic revision of the genus Digitaria (Panicoideae: Poaceae) in mainland Southeast Asia, Phytotaxa 246 (4), pp. 248-280 : 261-262

12. Digitaria longiflora (Retz.) Pers. (1805: 85) .— Paspalum longiflorum Retz. (1786: 15) . Type :— INDIA, Malabar, J.G. König s.n. in Herb. Retzius (holotype LD; isotypes BM!, K!).

Panicum propinquum R. Br. (1810: 193) .— D. propinqua (R. Br.) P. Beauv. (1812: 160, 170). Type :— AUSTRALIA, R. Brown 6122 (holotype BM!; isotypes E!, K!).

Digitaria malesiae Ohwi (1947: 6) . Type:— INDONESIA, Sumatra, H.A.B. Bünnemeijer 4137 (holotype BO!; isotypes L, U).

Digitaria curvipes Mez (1921: 8) . Type :— AUSTRALIA, Queenland, J. Dallachy s.n. (holotype B; isotypes BRI, K, L, MEL, NSW).

Digitaria oblongo-ovata Ohwi (1947: 7) . Type:— INDONESIA, Java, J. Ohwi 12 (holotype BO!).

Digitaria eriolepis Henrard (1950: 819) . Type :— AUSTRALIA, Queenland, Gulliver s.n. (holotype W; isotypes BRI, K).

Digitaria speciosa Henrard (1950: 837) . Type :— AUSTRALIA, Queenland, S.T. Blake 8383 (holotype L; isotypes BRI, K).

Annual or perennial. Culms tufted, sometimes rhizomatous, creeping or ascending, 50–75 cm high. Sheaths terete, glabrous, 3.3–5.5 cm long. Blades linear, 5–9 by 3.5–5 mm, both surfaces glabrous, apex acuminate. Ligules 1.2–1.5 mm long. Inflorescences composed of racemes; peduncles pilose; common axis absent. Racemes 2 or 3, longest 8–10 cm long, digitate; rachis ribbon-like, winged, 0.5–0.7 mm wide, margin spicular, spicules ca. 0.1 mm long. Pedicels terete, glabrous; abscission discoid to cupuliform. Spikelets ternate or more, sometimes a pedicel fused to the rachis, homomorphous, ovate-elliptic, 1.4–1.8 mm long; hairs verrucose with acute apex. Lower glume absent. Upper glume lanceolate, as long as the spikelet, chartaceous, apex acute, pubescent between nerves and on margins, nerves 5. Lower lemma as long as the spikelet, chartaceous, apex acute to acuminate pubescent between nerves with or without narrow glabrous interspaces beside the midnerve, nerves 7, inequidistant; palea absent or reduced to membranous, ca. 0.2 mm long. Upper lemma as long as the spikelet, elliptic, apex acute, yellowish. Anthers 0.6–1 mm long, yellowish to creamy. Caryopsis ellipsoid, 0.9–1 mm long, whitish creamy or purple. ( Figures 4E & 4F )

Distribution: —Common, tropical and subtropical regions of the Old World. Introduced in the New World.

Selected specimens examined: — CAMBODIA. Siem Reap: M. Schmid s.n. ( P). LAO PDR. Vientiane: Dong Dok , 2 May 2005, P. Sengsomphou OD 59 ( L) . MYANMAR: Kachin: Myitkyina, 25 November 1948, U T. Lwin 629 ( K). Mandalay: Pyin Oo Lwin , 14 July 1908, J. H. Lace 3920 ( K) ; ibid., 4 June 1938, D. Rhind 2317 ( K). Yangon: Yangon University, 7 August 1951, K. R. Ramachandran 252 ( K). Rakhine: Ramree Island , 26 May 1945, E. L. Wallace 158 ( K). PENINSULAR MALAYSIA. Kedah: Kuala Muda, 6 March 2010, M. Y. Chew, H. Duistermaat & A. Mohd. Nazri FRI 63646 ( KEP, L). Pahang: Gebeng, 25 September 2006, T. L. Yao, H. Duistermaat, R. Kiew & H. L. Kueh FRI 53027 ( KEP, L). Malacca: 17 July 1956, H. B. Gilliland 5121 ( SING) . THAILAND. Chiang Mai: Fang, 21 February 1958, Th. SØrensen, K. Larsen & B. Hansen 1419 ( BKF, E). Udon Thani: Ban Phue, 7 October 2010, B. Boonsuk 433 ( BK, BKF, KKU). Ubon Ratchathani: Sirinthon, Khan Rai, 26 July 2010, B. Boonsuk 342 ( BK, BKF, KKU). Prachuap Khiri Khan: Hua Hin, 6 November 1927, A. F. G. Kerr 13465 ( BK, BKF, BM, K). Saraburi: 28 May 1923, A. F. G. Kerr 7013 ( BK, BM, K). Chanthaburi: Ma Kham, 9 April 1959, T. Smitinand 5759 ( BKF, K). Surat Thani: Ko Tao, 31 December 1926, A. F. G. Kerr 11199 ( BK, BM, K). Trang: Si Kao, Mai Phat, 18 August 2010, B. Boonsuk 370 ( BK, BKF, KKU, QBG). Pattani: Cho Ai Rong, Bukit, 9 May 1923, A. F. G. Kerr 7140 ( BK, BM) . VIETNAM. Hanoi: Sontay , 1 November 1937, A. Pételot 2030 ( BO, P). Quang Ninh: Dam-Ha, 18 May 1940, W. T. Tsang 30000 ( BO, K, P). Thua Thien-Hue: 7 January 1916, Eberhardt 2206 ( P). Da Nang: 1 October 1921, A. S. Hitchcock 19409 ( P). Dac Lac: 9 November 1998, J. B. Hacker 1560 ( L). Binh Thanh: Bien Hoa, 8 September 1916, A. Chevalier 29988 ( P) .

Ecology: —Open and moist areas and open grassy pine forest; elevation 10–1,200 m.

Conservation status: — Digitaria longiflora is very common and has a widespread distribution. Therefore, we can designate this species with a rating of LC according to IUCN (2012) criteria.

Note: —The inflorescences of D. longiflora usually consist of pilose peduncles with 2–3 digitate racemes. Its upper florets are yellowish.

Figures

FIGURE 4. SEM micrographs of spikelets of some Digitaria species from mainland SE Asia. A–D. D. heterantha (from M. Norsaengsri 2827): A–B. subsessile spikelets; A. lower glume and lower lemma, lower lemma with closed nerves and slit-like interspaces between nerves; B. upper glume. C–D. pedicelled spikelets; C. lower glume and lower lemma, lower lemma pubescent with sericeous hairs and bristles; D. upper glume. E–F. D. longiflora (from B. Boonsuk 370): E. lower glume and lower lemma; F. upper glume. G–H. D. mollicoma (from B. Boonsuk 164): G. lower glume and lower lemma; H. upper glume. I–J. D. petelotii (from B. Boonsuk 98): I. lower glume and lower lemma; J. upper glume. K–L. D. pusilla (from A.F.G. Kerr 11198): K. lower glume and lower lemma; L. upper glume. Scale bar: A–D. & G–J. = 400 μm, E–F. & K–L. = 200 μm.