Digitaria sparsifructus Ohwi (1947: 7)

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 : 268

20. Digitaria sparsifructus Ohwi (1947: 7) . Type: — INDONESIA, Central Java, Rembang, C.A. Backer 6605 (holotype BO!; isotype K! fragm. in BRI; L).

Digitaria siamensis Henrard (1950: 692) . syn. nov. Type:— THAILAND, Kanchanaburi, A.J.G.H. Kostermans 1359 (holotype L!; isotype K!).

Annual. Culms small tufted, erect to geniculately ascending, not rooting at nodes, up to 75 cm high. Sheath s 2.5 –5 cm long, not breaking to fibres at base, glabrous or setose on margins. Ligules 1–2 mm long. Blades linear, 6–25 cm by 3–6 mm, chartaceous, apex acuminate; margin entire; both surfaces glabrous. Inflorescences composed of racemes; peduncles glabrous; common axis 0.5–5 cm long. Racemes 4–10, longest 8–12 cm long, subdigitate or alternate along the common axis; rachis triquetrous, filiform, not winged, 0.3–0.4 mm wide, serrate. Pedicels triquetrous, serrate; abscission discoid to cupuliform. Spikelets binate, ternate or in groups of four spikelets, homomorphous, elliptic, 1.9–2.2 mm long; hairs smooth with clavate apex. Pedicels flattened to terete, serrulate; abscission discoid. Lower glume absent. Upper glume elliptic, as long as spikelets or slightly shorter, elliptic, chartaceous, apex acute, nerves 3. Lower lemma as long as the spikelet, chartaceous, apex acute, pubescent between nerves but with narrowly glabrous interspace beside the midnerve, nerves 5–7, inequidistant. Upper lemma as long as the spikelet, chartaceous, apex acute, not protruding above the lower lemma, brown to dark brown. Anthers 0.4–0.7 mm long. Caryopsis ellipsoid, 0.7–0.8 mm long, brownish.

Distribution: — Myanmar, Thailand, Lao PDR, Cambodia, Vietnam, Indonesia.

Selected specimens examined: — CAMBODIA. Kampong Cham: M. Schmid VN 1476 ( P). LAO PDR. Champasak: Mae Khong river , 11 September 1998, J. F. Maxwell 98-890 ( L, Herb. Biology, Chiang Mai University). MYANMAR. Mandalay: Popa, 10 September 1938, D. Rhind 2625 ( K, L). THAILAND. Lamphun: Ban Hong, 22 Aug. 2004, S. Sirimongkol 141 ( BKF). Loei: Phu Kradueng, 27 August 1988, H. Koyama T-61349 ( BKF). Khon Kaen, Phu Pha Man NP, 26 September 2010, B. Boonsuk 429 ( BK, BKF, KKU). Chaiyaphum: Phu Khiao, 24 July 1994, M. Norsaengsri 296 ( QBG). Suphanburi: Doem Bang Nang Buat, 21 September 1930, A. F. G. Kerr 19704 ( BK, BM, K). Saraburi: Mueang, Sam Lan Forest , 30 June 1974, J. F. Maxwell 74-652 ( AAU, BK) ; Chon Buri: VIETNAM. Dac Lac: Khanh Hoa, 20 September 1954, M. Schmid VN 2317 ( P) .

Ecology: —Deciduous and pine forests; elevation 200–1,000 m.

Conservation status: — Digitaria sparsifructus is distributed almost throughout SE Asia; hence it is categorized as LC, according to IUCN (2012) criteria.

Note: — Digitaria siamensis , reported in Myanmar and Thailand ( Henrard, 1950; Nanakorn & Norsaengsri 2001, Kress et al. 2003), is closely similar to D. sparsifructus from Indonesia in its habit, inflorescence and size and shape of spikelets. The lower glume of D. sparsifructus is a minute membrane up to 0.1 mm long or can be absent and its upper glume is as long as the spikelets, whereas D. siamensis has no lower glume and its upper glume is found in the range of slightly shorter than to as long as the spikelet. Therefore, D. siamensis is best treated as a synonym of D. sparsifructus . In addition, we found that the lower lemma of the type specimens of D. sparsifructus have glabrous interspaces beside the midnerve but the illustration of the spikelet by Henrard (1950) shows pubescence throughout the lower lemma.