Digitaria cruciata (Nees ex Steud.) A. Camus var. cruciata

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 : 256-257

5.1 Digitaria cruciata (Nees ex Steud.) A. Camus var. cruciata

Annual. Culms small tufted, ascending to erect, 15–60 cm high; nodes and internodes glabrous; cataphylls absent. Sheaths 3–5.5 cm long, glabrous. Ligules 2.5–4 mm long. Blades linear, 4.5–10 cm by 5–10 mm, apex acuminate, margin serrate and sinuate at one side, both surfaces glabrous to scabrous with or without bulbous based hairs. Inflorescences composed of racemes; peduncles glabrous; common axis 0–7 cm long. Racemes 2–11, longest 3– 10 cm long, digitate, subdigitate or alternate along the common axis; rachis ribbon-like, winged, ca. 1 mm wide, serrate. Pedicels triquetrous, serrate; abscission truncate. Spikelets binate, homomorphous, broadly elliptic, turgid, 2.2–3 mm long, slightly glabrous; hairs smooth with acute apex. Lower glume ovate or triangular, 0.2–0.3 mm long, membranous, apex acute, glabrous. Upper glume elliptic, 1–2 mm long, membranous, apex emarginate or truncate, glabrous or pubescent with sericeous hairs at the margin, nerves 3. Lower lemma elliptic, shorter than the spikelets, chartaceous, apex acute to acuminate, glabrous or pubescent with sericeous hairs at the margin, nerves 7 with broad interspaces beside the midnerve, inequidistant. Upper lemma turgid, 2.5–3.2 mm long, protruding above the lower lemma, chartaceous, greyish to yellowish. Anther s 0.8 –0.9 mm long, yellowish. Caryopsis oblong-ellipsoid, ca. 1.5 mm long, creamy.

Distribution: — India, Nepal, China, Vietnam.

Selected specimens examined: — VIETNAM. Lao Cai: Sa Pa , 11 September 2005, V. X. Phuong, D.D. Huyen, N. V. Du, N. Q. Binh, D. T. Xuyen, R. de Kok, G. Bramley, G. Challen & M. Vorontsova HNK 28 ( K) ; ibid., 11 January 1912, M. Hautefeuille s.n. ( P) .

Ecology: —Grasslands and scrub on high mountains; elevation up to 1,700 m.

Conservation status: —This Himalayan species is only known from one locality in the north of Vietnam. Its conservation status is assessed as Data Deficient (DD), according to IUCN (2012) criteria.

Note: — Digitaria cruciata is distinguished by its broadly elliptic and turgid spikelets. The upper glume usually protrudes above the lower lemma.

5.2 Digitaria cruciata (Nees ex Steud.) A. Camus var. pectinata Veldkamp (1973: 72) . Type :— INDIA, Khasia, W. Griffith KD 6574 (holotype W! ( W0010057 ); isotype W! ( W19160021560 )).

Annual, small tufted. Blades linear, 6–10 cm by 4–6 mm, apex acuminate. Inflorescences composed of racemes; common axis 0–5 cm long. Racemes 2–12, longest 5–14 cm long, digitate, subdigitate or alternate along the common axis; rachis ribbon-like, winged, ca. 1 mm wide, serrate. Pedicels triquetrous, serrate; abscission truncate. Spikelets binate, homomorphous, broadly elliptic, turgid, 2.2–2.5 mm long. Lower glume ovate or triangular, 0.2–0.3 mm long, membranous, apex acute, glabrous. Upper glume elliptic, 1–2 mm long, membranous, apex emarginate or truncate, glabrous or pubescent at the margin, nerves 3. Lower lemma pubescent with bulbous base bristles, in pectinate form. Upper lemma protruding above the lower lemma, acuminate.

Distribution: — India, Vietnam.

Ecology: —As the typical variety.

Conservation status: —This variety was recorded from only two localities from the Khasi Hills, India and Sa Pa (Cha-Pa), N Vietnam (Veldkamp 1973). Its conservation status is assessed as Data Deficient (DD), according to IUCN (2012) criteria.

Note: —This variety is very similar to the typical variety in habit and inflorescences but differs in spikelets having bulbous base bristles on lower lemma, occurring in pectinate form.