Digitaria larsenii Bor (1962: 157)

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 : 261

11. Digitaria larsenii Bor (1962: 157) . Type:— THAILAND, Chiang Mai, Th. SØrensen, K. Larsen & B. Hansen 4607 (holotype L!; isotypes BK!, C!, K!).

Annual. Culms small decumbent and branching, 15–60 cm high, nodes pilose. Sheaths 2–3 cm long, not breaking to fibres at base, densely pilose with bulbous based hairs. Ligules 1–1.5 mm long. Blades linear, 7–10 cm by 2–3 mm, margin scabrous; upper surface scabrous with sparsely bulbous based hairs. Inflorescences composed of racemes; peduncles glabrous; common axis 0.7–1.5 cm long. Racemes 3–4, longest 2–5 cm long, subdigitate or alternate along the common axis; rachis filiform, triquetrous, not winged, ca. 0.2 mm wide, serrate. Pedicels triquetrous, serrulate; abscission discoid to cupuliform. Spikelets ternate at least in the lower part and binate in the upper part of racemes, homomorphous, lanceolate-elliptic, 1.7–1.8 mm long, appressed on the rachis; hairs smooth with clavate apex. Lower glume absent. Upper glume elliptic, 1.2–1.3 mm long, apex acute, pubescent between nerves, nerves 3. Lower lemma 1.5–1.6 mm long, membranous, apex acute, pubescent between nerves but with narrow glabrous interspaces beside the midnerve, nerves 5, equidistant. Upper lemma as long as the spikelet, protruding above the lower lemma, chartaceous, apex acute, brown, often with pale apex. Anthers 0.5–0.7 mm long, yellow. Caryopsis ellipsoid, 0.6–0.8 mm long, yellowish.

Distribution: —Endemic to Thailand.

Selected specimens examined: — THAILAND. Chiang Mai: Doi Suthep , 29 August 1958, Th. SØrensen, K. Larsen & B. Hansen 4607 ( BK, C, K, L) ; ibid., 12 October 2001, S. Laegaard & M. Norsangsri 21702 ( AAU) .

Ecology: —On rocks; elevation ca. 700 m.

Conservation status: — Digitaria larsenii is uncommon and only known from one locality in Chiang Mai province, Thailand. We assess its conservation status with the provisional rating of Endangered (EN), according to IUCN (2012) criteria.

Note: — Digitaria larsenii is endemic to Thailand. It is similar to D. abludens but differs in having non-spreading pedicels, longer spikelets and more protruding upper florets.