Digitaria setigera Roth ex Roem. & Schult. var. setigera

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 : 266-268

19.1 Digitaria setigera Roth ex Roem. & Schult. var. setigera

Annual or perennial. Culms loosely tufted, ascending to erect or decumbent, 70–110 cm high, rooting at lower nodes; nodes and internodes glabrous; cataphylls absent. Sheaths 5.5–7.5 cm long, setose. Blades linear, 12–25 cm by 8–12 mm, apex acute, margin hispid, both surfaces scaberulous with bulbous based hairs. Ligules 2.2–4 mm long. Inflorescences composed of racemes; peduncles glabrous; common axis 0–8 cm long. Racemes (2–)5–9(–16), longest 12–16 cm long, digitate or subdigitate; rachis ribbon-like or triquetrous, winged, serrate, 0.6–0.8 mm wide. Pedicels triquetrous, spicular; abscission truncate. Spikelets binate, homomorphous, lanceolate, 2.8–3.2 mm long; hairs smooth with acute apex. Lower glume absent. Upper glume ovate to elliptic, 0.7–0.8 mm long, chartaceous, apex obtuse, pubescent between nerves and on margin with overtopping hairs, nerves 3. Lower lemma lanceolate, 2.8–3.2 mm long, chartaceous, apex acute, pubescent between nerves and on margin but with broad glabrous interspaces beside the midnerve, composed of sericeous hairs only, nerves 7, inequidistant. Upper lemma lanceolate, 2.4–2.5 mm long, chartaceous, apex acute, not protruding above the lower lemma, greyish to yellowish. Anthers 1–1.2 mm long. Caryopsis ellipsoid, ca. 1.7 mm long, brownish.

Distribution: — Pakistan, Bhutan, India, Sri Lanka, China, Myanmar, Thailand, Lao PDR, Cambodia, Vietnam, Malaysia, Indonesia, Philippines, Papua New Guinea, Pacific, Australia, introduced elsewhere, e.g. America.

Selected specimens examined: — CAMBODIA. Ratanakiri: Ban Tuh, 9 January 1969, M.A. Martin 1410 (P). LAO PDR. Attapeu: 3 October 2010, B. Boonsuk & S. Lanosavanh 442 (KKU, Biology Herbarium NUOL). MYANMAR. Mandalay: 9 October 1941, D. Rhind 3493 (K). Bago: 20 July 1948, U T. Lwin 586 (K). Yangon: 11 May 1932, C.E. Parkinson 14401 (K). Tanintharyi: 15 October 1961, J. Keenan, U T. Aung & R.H. Rule 1659 (K). PENINSULAR MALAYSIA. Kedah: Kampong Naka, 9 September 1933, R.E. Holttum SF 28402 (K, P, SING). Penang: Kuala Tahan, 30 November 1920, E. Seimund 313 (SING). Kelantan: Gua Musang, 28 September 2006, T.L. Yao, H. Duistermaat, R. Kiew & H.L. Kueh FRI 53176 (KEP, L). Terengganu: Kuala Terengganu, 26 September 2006, T.L. Yao, H. Duistermaat, R. Kiew & H.L. Kueh FRI 53113 (KEP, L). THAILAND. Chiang Mai: Chom Thong, Doi Inthanon National Park, 6 November 2011, B. Boonsuk 596 (KKU). Phitsanulok: Phu Hin Rong Kla National Park, 6 December 2009, B. Boonsuk 205 (KKU). Sakon Nakhon: Phu Phan National Park, 4 October 2009, B. Boonsuk 171 (KKU). Si Sa Ket: Khun Han, 12 December 2009, B. Boonsuk 209 (KKU). Ayutthaya: 10 August 1984, Vacharee 602 (BK). Trat: Ko Chang, 17 March 2011, B. Boonsuk 573 (KKU). Ranong: Kraburi, Pak Chan, 17 January 1987, J. Supapol 273 (PSU). Songkhla: Ko Yo, 14 August 2010, B. Boonsuk 356 (KKU). Pattani: Khao Kala Kiri, 29 March 1928, A.F.G. Kerr 14865 (BK, BM, K). VIETNAM. Yen Bai: Yen Binh, 20 April 1983, L.C. Chae C06 (K). Thua Thien-Hue: Hue, July 1927, J. & M.S. Clemens 3104 (BM). Vinh Phuc: 4 December 2010, B. Boonsuk 503 (KKU), 504 (KKU). Lam Dong: 3 May 1954, M. Schmid VN 1744 (P).

Ecology: —Open grassy areas, along roadsides; elevation 500–2,750 m.

Conservation status: — Digitaria setigera var. setigera is a common taxon and has a widespread distribution. Therefore, we place the variety in the category rating of LC according to IUCN (2012) criteria.

Note: — Digitaria setigera var. setigera is easily recognised by the absence of a lower glume and its small upper glume which is shorter than half the length of the spikelet.

19.2 Digitaria setigera Roth ex Roem. & Schult. var. calliblepharata (Henrard)Veldkamp (1973: 40) .— D. microbachne (J. Presl) Henrard subsp. calliblepharata Henrard (1950: 452) .— D. microbachne (J. Presl) Henrard var. calliblepharata Henrard ex Henty (1969: 77) . Type:— INDONESIA, Java, C.A. Backer 27997 (holotype: L; isotype BO!).

Annual or perennial. Culms loosely tufted, 70–100 cm high, ascending to erect or decumbent, rooting at lower nodes; nodes and internodes glabrous; cataphylls absent. Sheaths 3–6.5 cm long, pilose with bulbous based hairs. Blades linear, 6–10 cm by 5–7.5 mm, apex acuminate, margin serrulate, both surfaces scaberulous. Ligules 2–2.2 mm long. Inflorescences composed of racemes; peduncles glabrous; common axis (0–) 2–5 cm long. Racemes 3–12, longest 9–12 cm long, digitate to subdigitate; rachis triquetrous and winged, 0.5–0.6 mm wide, serrate. Pedicels triquetrous, spiculate; abscission truncate. Spikelets binate, homomorphous, lanceolate, 3–3.2 mm long, apex acute, composed of sericeous hairs and glassy bristles. Lower glume absent or triangular, 0.1–0.2 mm long. Upper glume ovate, 0.4– 0.6 mm long, pubescent membranous, along nerves, apex obtuse, nerves 3. Lower lemma lanceolate, as long as the spikelet, chartaceous, apex acute, pubescent between nerves and on margin but with broad glabrous interspaces beside the midnerve, composed of sericeous hairs and usually bulbous based bristles, nerves 7, inequidistant. Upper lemma lanceolate, 2.4–2.5 mm long, chartaceous, apex acute, not protruding above the lower lemma, yellowish to brownish. Anthers 3, 0.9–1 mm long, yellowish. Caryopsis ellipsoid, 1–1.5 mm long, pale creamy.

Distribution: — India, Thailand, Malay Peninsula, Singapore, Indonesia, Philippines, Guam.

Selected specimens examined: — PENINSULAR MALAYSIA. Malacca: Hair s.n. ( SING). THAILAND. Loei: Nong Hin , 13 September 2009, B. Boonsuk 137 ( BKF, KKU) ; Phu Kradueng National Park , 8 November 2010, B. Boonsuk 463 ( KKU) ; Nakhon Phanom: Renu Nakhon , 27 February 2010, B. Boonsuk 219 ( KKU) .

Ecology: —Open areas, sandy soils; elevation 200–600 m.

Conservation status: — Digitaria setigera var. calliblepharata is assessed as LC (same as the typical variety) according to IUCN (2012) criteria.

Note: — Digitaria setigera var. calliblepharata is recognised by its glassy bristles on its lower lemma which usually have bulbous bases ( Boonsuk et al. 2014a). The lower glume is usually absent in most specimens from Indonesia but it is clearly present in the specimens from Thailand.