Digitaria nuda Schumach. (1827: 45)

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 : 262-263

14. Digitaria nuda Schumach. (1827: 45) . Type :— GHANA, P. Thonning 367 (holotype C!; isotype L!).

Digitaria borbonica Desv. (1831: 167) . Type:— FRANCE, Réunion, N.A. Desvaux s.n. (not located).

Annual. Culms small or loosely tufted, ascending to erect, 30–50 cm high, rooting at lower nodes; nodes and internodes glabrous; cataphylls absent. Sheaths pilose in lower part, 3–6.5 cm long. Blades linear, 3–5 cm by 2.5–4 mm, both surfaces scabrous, apex acuminate. Ligules 0.8–1 mm long. Inflorescences composed of racemes; peduncles glabrous; common axis 0–2.5 cm long. Racemes 4–7, longest 6–9 cm long, digitate to subdigitate; rachis ribbon-like, winged, 0.5–0.6 mm wide, serrate, midrib triquetrous, setose along the raceme, Pedicels triquetrous, margin serrate; abscission truncate. Spikelets binate, homomorphous, elliptic-lanceolate, 2–2.5 mm long; hairs smooth with acute apex. Lower glume absent. Upper glume chartaceous, lanceolate, 1.5–1.8(–2) mm long, pubescent between nerves, nerves 3. Lower lemma lanceolate, as long as the spikelet, chartaceous, apex acute to acuminate, pubescent between nerves and on margins but with broad glabrous interspaces beside the midnerve, nerves 7, inequidistant. Upper lemma 1.8–2 mm long, chartaceous, apex acuminate, not protruding above the lower lemma, yellowish to brownish. Anthers 0.5–0.8 mm long, brown. Caryopsis ellipsoid, ca. 1.5 mm long, dark brown. ( Figures 3K & 3L )

Distribution: —Common, tropical regions.

Selected specimens examined: — MYANMAR. Yangon: Hlegu, 26 December 1986, Y. Paisooksantivatana y- 2010-86 (BK). PENINSULAR MALAYSIA. Pahang: Cameron Highlands, 25 May 1931, C.F. Symington 20843 (KEP). Selangor: Kepong, 23 August 1927, E.J. Strugnell 13185 (KEP). THAILAND. Pha Yao: Mae Chai, 16 July 2010, B. Boonsuk 321 (KKU). Phetchabun: Khao Kho, Nong Mae Na, 10 June 2010, B. Boonsuk 286 (KKU). Bueng Kan: Bueng Khong Long, 28 November 2010, B. Boonsuk & P. Phonsena 499 (KKU). Chaiyaphum: Phu Khiao Wildlife Sanctuary, 24 July 1994, M. Norsaengsri 286 (QBG). Rachaburi: Suan Phueng, 2 August 2009, B. Boonsuk 123 (BK, BKF, KKU). Rayong: Ko Sa Met, 18 March 1970, C. F. van Beusekom & T. Santisuk 3247 (AAU, BKF, C, E, K, L, P). Surat Thani: Kanchanadit, 11 May 1987, Y. Paisooksantivatana y-2157-87 (BK). Songkhla: Kho Hong, 6 May 1970, S. Sutheesorn 1660 (BK). VIETNAM. Binh Thanh: Bien Hoa, 22 March 1954, M. Schmid s.n. (P).

Ecology: —Open grassy areas; elevation 100–800 m.

Conservation status: — Digitaria nuda is one of the common species in the Mainland SE Asia. Therefore, we can provide this species in rating of Least Concern (LC), according to IUCN (2012) criteria.

Note: —The inflorescence of D. nuda is usually setose along the rachis. Its spikelets are similar to D. ciliaris in its upper glume features and to D. setigera in its absent lower glume. However, its spikelets are smaller than those of both species.

Figures

FIGURE 3. SEM micrographs of spikelets of some Digitaria species from mainland SE Asia. A–B. D. abludens (from S. Laegaard & M. Norsangsri 21666): A. lower lemma; B. upper glume. C–D. D. fuscescens (from B. Boonsuk 627): C. lower lemma; D. upper glume. E–H. D. bicornis (from B. Boonsuk 341): E–F. subsessile spikelets; E. lower glume and lower lemma; F. upper glume. G–H. pedicelled spikelets; G. lower glume and lower lemma, sericeous hairs and bristles on lower lemma; H. upper glume. I–J. D. ciliaris (from B. Boonsuk 375): I. lower glume and lower lemma; J. upper glume. K–L. D. nuda (from B. Boonsuk 286): K. lower glume; L. upper glume. Scale bar: A–D = 200 μm, E–L = 400 μm.