Digitaria stricta Roth ex Roem. & Schult. (1817: 474)

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 : 268-269

21. Digitaria stricta Roth ex Roem. & Schult. (1817: 474) . Type:— INDIA, B. Heyne s.n. (holotype B).

Distribution: — Pakistan, India, Bhutan, Nepal, and China. One variety is found in the north of Thailand.

21.1. Digitaria stricta Roth ex Roem. & Schult. var. glabrescens Bor (1955: 336) .— D. glabrescens (Bor) L. Liu. (1990: 320) . Type:— INDIA, Khasia, J.D. Hooker & T. Thomson s.n. (lectotype K!), designated here.

Annual. Culms tufted or solitary, not rhizomatous, erect, (10–)20–50(–110) cm high; nodes glabrous, brown, not rooting at nodes. Sheath s 2.5 –4 cm long, glabrous. Ligules 0.6–1 mm long. Blades linear, 6–14 cm by 0.3–0.4 mm, chartaceous, apex acute to acuminate, both surfaces glabrous. Inflorescences composed of racemes; peduncles glabrous; common axis 0.5–5 cm long. Racemes 2–5(–11), longest 6–14(–18) cm long, subdigitate; rachis ribbon-like, winged, 0.5–0.6 mm wide, serrate. Pedicels flattened to terete, serrate, longest pedicels as long as the length of spikelet, with elongate spicules up to 1 mm long; abscission discoid. Spikelets ternate, homomorphous, elliptic to ovate, (0.8–) 1.2– 1.4 mm long, apex acute, absolutely glabrous to glabrescent with clavate hairs. Lower glume absent. Upper glume ovate, 0.2–0.3 mm long, membranous, apex obtuse, glabrous, nerves 0–3. Lower lemma elliptic, as long as the spikelet, chartaceous, apex acute, glabrescent to absolutely glabrous, nerves 3–5. Upper lemma 1.1–1.2 mm long, coriaceous, apex acute, dark purple to blackish. Anthers ca. 0.3 mm long, yellowish. Caryopsis oblong-ellipsoid, 0.7–0.8 mm long, pale creamy. ( Figures 5E & 5F )

Distribution: — Pakistan, India, Nepal, Bhutan, China, Thailand.

Selected specimens examined: — THAILAND. Chiang Mai: Doi Chiang Dao Wildlife Sanctuary , 18 January 1989, W. Nanakorn 2294 ( QBG) ; Doi Fa Hom Pok National Park , 21 November 2010, B. Boonsuk & P. Phonsena 478 ( BK, BKF, KKU, QBG) .

Ecology: —Lower montane scrubs; elevation up to 1,000 m.

Conservation status: —This Himalayan species is found in the north of Thailand. Its conservation status is assessed as DD, according to IUCN (2012) criteria.

Note: — Digitaria stricta var. glabrescens is distinguished by its spicules or bristles on pedicels, its membranous upper glume and its blackish upper florets. The typical variety has densely clavate or clavate hairs whereas the variety glabrescens has glabrous spikelets.

Figures

FIGURE 5. SEM micrographs of spikelets of some Digitaria species from mainland SE Asia. A–B. D. radicosa (from B. Boonsuk 216): A. lower glume and lower lemma; B. upper glume. C–D. D. setifolia (from B. Boonsuk 232): C. lower glume and lower lemma; D. upper glume. E–F. D. stricta var. glabrescens (from B. Boonsuk 478): E. lower lemma; F. upper glume and upper lemma. G–H. D. ternata (from B. Boonsuk 330): G. lower glume and lower lemma; H. upper glume. I–J. D. tomentosa (from J.F. Maxwell 05-484): I. lower lemma; J. upper glume and upper lemma. K–L. D. violascens (from B. Boonsuk 297): K. lower lemma; L. upper glume. Scale bar: A–D. & G–J. = 400 μm, E–F. & K–L. = 200 μm.