Digitaria thailandica B. Boonsuk, Chantar. & Hodk. (2014a: 283)

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 : 270

23. Digitaria thailandica B. Boonsuk, Chantar. & Hodk. (2014a: 283) . Type:— THAILAND, Loei, B. Boonsuk 590 (holotype KKU!; isotypes BK!, BKF!, K!).

Perennial. Culms tufted, rhizomatous, decumbent or ascending to erect, 75–120 cm high, rooting at lower nodes; nodes and internodes glabrous. Sheaths 4–12 cm long, usually longer than internodes, glabrous to pilose on upper surface. Ligules 2–6 mm long. Blade s linear, 6–20 cm by 5–15 mm, chartaceous, apex acuminate, margin sinuate; both surfaces scabrous, sometimes with bulbous based hairs. Inflorescences composed of racemes; common axis 2.5–6 cm long; peduncles glabrous. Racemes 7–13, longest 9–21 cm, verticillate and subdigitate; rachis triquetrous, 0.3–0.5 mm wide, serrate, setose upwards. Pedicels triquetrous, spicular; abscission slightly cupuliform to truncate. Spikelets binate, homomorphous, lanceolate, 3–3.2 mm long; hairs smooth with acute apex. Lower glume a triangular scale, 0.25–0.3 mm long, membranous, apex acute. Upper glume oblong, 0.5–1 mm long, chartaceous, apex truncate to slightly emarginate, hairy along the margins. Lower lemma as long as the spikelet, chartaceous, apex acute, pubescent with broad glabrous interspaces beside the midnerve, nerves 7, inequidistant; palea membranous, 0.6–0.8 mm long. Upper lemma 2.5–2.7 mm long, apex acuminate, brown. Anthers 1–1.4 mm long, yellowish to brownish. Caryopsis ellipsoid, 1.5–1.8 mm long, yellowish.

Distribution: —Endemic to Thailand.

Selected specimens examined: — THAILAND. Uthai Thani: Huai Kha Khaeng Wildlife Sanctuary, 18 July 1991, K. Chayamarit 550 ( BKF). Phitsanulok: Phu Hin Rong Kla National Park, 11 September 2010, B. Boonsuk, P. Phonsena & P. Kochaiphat 409 ( BK, BKF, KKU, QBG). Loei: Phu Ruea National Park , 11 October 2009, B. Boonsuk 147 ( KKU, QBG) ; San Tom, 3 November 2011, B. Boonsuk 590 ( BK, BKF, KKU, K). Phetchabun: Nam Nao National Park , 22 January 2011, B. Boonsuk 558 ( BK. BKF, KKU) .

Ecology: —Shade of evergreen and deciduous forests; elevation 300– 600 m.

Conservation status: —This species is found only in a small area in northern and northeastern Thailand. The conservation status should be assessed as Near Threatened (NT), according to according to IUCN (2012) criteria.

Note: —This species is distinguished by its long common axis, setae along the racemes, and truncate upper glume which is shorter than half the length of the spikelets. It is similar to D. junghuhniana and D. thyrsoidea but differs in having setae on the racemes, triangular lower glumes, truncate upper glumes with three nerves and broad glabrous interspaces on either side of midnerve of lower glume ( Boonsuk et al. 2014a).