Digitaria abludens (Roem. & Schult.) Veldkamp (1973: 53)

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 : 252-254

1. Digitaria abludens (Roem. & Schult.) Veldkamp (1973: 53) .— Panicum abludens Roem. & Schult. (1817: 457) . Type :— INDIA, B. Heyne s.n. in Herb. Roth (holotype B†; isotypes BM!, K!).

Paspalum granulare Trin. (1821: 47) .— D. granularis (Trin.) Henrard (1950: 302) . Type :— INDIA, J.G. König in Herb. Trinius 467.1 (holotype LE; isotype Herb. Banks ex Herb. Jacquin BM).

Paspalum pedicellare Trin. ex Hook.f. (1896: 19) .— D. pedicellaris (Trin. ex Hook.f.) Prain (1903: 1182) . Type :— INDIA, W. Roxburgh s.n. (holotype BM!; isotypes K!).

Annual. Culms small tufted, erect to geniculate, up to 75 cm high; nodes and internodes glabrous. Sheath s 2.5 –5 cm long, not breaking to fibres at base, glabrous. Ligules 1.4–1.6 mm long. Blades linear, 4–12 cm by 2–3 mm, chartaceous, apex acuminate, both surfaces glabrous. Inflorescences composed of racemes; peduncles glabrous; common axis 0.5–5 cm long. Racemes 3–10, longest 6–12 cm long, subdigitate or alternate along the common axis; rachis filiform, triquetrous, not winged, ca. 0.2 mm wide, serrate. Pedicels flattened to terete, serrulate, usually patent; abscission cupuliform to discoid. Spikelets ternate at least in the lower part of the racemes, homomorphous, elliptic, 1.3–1.6 mm long, not appressed on the rachis; hairs smooth with clavate apex. Lower glume absent. Upper glume elliptic, 1.2–1.3 mm long, chartaceous, apex acute, pubescent between nerves and on margins, nerves 3. Lower lemma elliptic, 1.2–1.4 mm long, chartaceous, apex obtuse, pubescent between nerves and on margin, nerves 7, equidistant. Upper lemma as long as the spikelet, dark brown to dark purple, protruding above the lower lemma. Anthers 0.4–0.7 mm long. Caryopsis ellipsoid, ca. 1 mm long, brown. ( Figures 3A & 3B )

Distribution: — Pakistan, Nepal, Bhutan, India, Sri Lanka, Myanmar, Thailand, Indonesia, Philippines, Papua New Guinea.

Selected specimens examined: — MYANMAR. Kachin: 25 June 1947, U T. Lwin 97 ( K) ; Mandalay: Yemethin, 21 August 1938, D. Rhind 2491 ( K). Sagaing: Chinwin , 9 August 1908, J. H. Lace 4172 ( K) . THAILAND. Chiang Mai: Khun Wang , 3 October 2001, S. Laegaard & M. Norsangsri 21666 ( AAU, BKF, K, QBG). Nong Bua Lam Phu: Si Bun Rueang, 14 August 2005, S. Sirimongkol 189 ( BKF). Nakhon Ratchasima: Pak Chong, 5 September 1965, T. Smitinand & H. Sleumer 8357 ( BO, K, L, SING) ; Wang Nam Khiao, 17 September 2013, B. Boonsuk 697 ( BK, BKF, KKU). Kanchanaburi: 13 September 1931, A. F. G. Kerr 20555 ( BK, BM, K, L). Chon Buri: Si Racha , 4 September 1975, J. F. Maxwell 75-991 ( AAU, BK, L) .

Ecology: —Deciduous dipterocarp forest, roadsides; elevation up to 450 m.

Conservation status: —This species is widespread from South to Southeast Asia. Its conservation status is assessed as Least Concern (LC), according to IUCN (2012) criteria.

Note: — Digitaria abludens is distinguished by its dark brown and protruding upper florets. The pedicels usually spread from the rachis and length of the longest pedicel in each group is about two times the length of the spikelet.

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.