Digitaria in Flora of China @ efloras.org

175. Digitaria Haller, Hist. Stirp. Helv. 2: 244. 1768.

马唐属 ma tang shu

Authors: Shou-liang Chen & Sylvia M. Phillips

Leptoloma Chase; Syntherisma Walter.

Annual or perennial. Culms erect or decumbent, occasionally stoloniferous. Leaf blades linear or linear-lanceolate; ligule membranous. Inflorescence of digitately arranged racemes, sometimes on a short axis or with secondary branchlets, very rarely paniculate; spikelets usually in groups of 2–3(–4), imbricate to effuse, the latter often on notably long and unequal pedicels. Spikelets puberulous to villous, typically in stripes between the well-defined veins, rarely glabrous; lower glume absent or reduced to a little scale up to 1/4 spikelet length; upper glume variable; lower lemma usually ± equal to spikelet; upper floret pallid to black, apex subacute to acuminate, rarely apiculate. x = 9.

About 250 species:tropical and warm-temperate regions of the world; 22 species (three endemic) in China.

Digitaria has been traditionally divided on the nature of the spikelet hairs, which may be clavate, capitate, verrucose (warty, appearing beaded), or with crooked tips. As good magnification is required to see these features, the grouping of the spikelets on the raceme is a more practical aid to identification. Many species have regularly paired spikelets, which present no difficulty. In those species where the spikelets are grouped in clusters of 3 or more, care must be taken, as often the longest pedicel of a group is partially fused to the rachis so that the spikelets appear alternately paired and single, or sometimes one spikelet may be vestigial, or the spikelets may be paired toward the raceme tips.

Many species are very variable in spikelet pubescence and lemma nervation, even within a single raceme. Additionally, there are a number of complexes of intergrading species, so intermediates may occasionally be encountered. This has led to the publication of many superfluous names.

1 Inflorescence an open panicle with long capillary branches. 1 D. fujianensis

+ Inflorescence composed of racemes (2)

2 (1) Spikelets of a pair heteromorphic, lower spikelet glabrous or almost so, upper spikelet conspicuously hairy (3)

+ Spikelets all similar (5)

3 (2) Annual; midrib of rachis narrow, clearly winged; lower lemma with 7 slender veins. 10 D. ciliaris

+ Perennial and stoloniferous or annual; midrib of rachis thick, scarcely winged; lower lemma with 7–11 thick, prominent veins (4)

4 (3) Perennial, stoloniferous; spikelets 4–4.5 mm, spaced on rachis. 3 D. heterantha

+ Annual; spikelets ca. 3 mm, imbricate on rachis. 4 D. bicornis

5 (2) Tussocky perennial; leaf sheaths breaking up into fibers at base. 2 D. fibrosa

+ Annuals or short-lived perennials; leaf sheaths not forming fibrous tussock (6)

6 (5) Spikelets paired; pedicels with truncate tips (7)

+ Spikelets in groups of 3 or more, at least in middle part of raceme (sometimes a pedicel fused to the rachis, or a spikelet abortive, or if paired pedicels long and flexuous); pedicels usually with discoid tips (12)

7 (6) Lower glume absent or almost so. 5 D. setigera

+ Lower glume small but clearly present (8)

8 (7) Raceme rachis with smooth margins; racemes 2–3. 6 D. radicosa

+ Raceme rachis with scabrous margins; racemes often more than 3 (9)

9 (8) Upper glume 1/3–1/2 length of spikelet (10)

+ Upper glume 1/2–3/4 length of spikelet; lateral veins of lower lemma smooth; upper lemma not exceeding lower lemma (11)

10 (9) Lateral veins of lower lemma scabrous toward apex; upper glume subacute; upper lemma acuminate, equaling lower lemma. 7 D. sanguinalis

+ Lateral veins of lower lemma smooth; upper glume rounded; upper lemma apiculate, exceeding lower lemma. 8 D. cruciata

11 (9) Racemes erect, forming a narrow fascicle; spikelets 2.2–2.8 mm. 9 D. henryi

+ Racemes widely spreading at maturity; spikelets 2.5–3.5 mm. 10 D. ciliaris

12 (6) Spikelets with capitate or clavate hairs (if glabrous, pedicel tips hairy) (13)

+ Spikelets with smooth or verrucose hairs (tips sometimes coiled), or glabrous; pedicel tips glabrous (18)

13 (12) Tips of pedicels with a circlet of stiff, overtopping hairs or spicules up to 1 mm (14)

+ Tips of pedicels without overtopping hairs or spicules (15)

14 (13) Spikelets 1.8–2.5 mm; upper glume 2/3–4/5 spikelet length. 11 D. ternata

+ Spikelets 1.2–1.5 mm; upper glume 1/4–1/2 spikelet length. 12 D. stricta

15 (13) Rachis of raceme flat, winged; spikelets 2–2.2 mm. 20 D. ischaemum

+ Rachis of raceme slenderly triquetrous, not or scarcely winged; spikelets 1.3–2 mm (16)

16 (15) Spikelets 1.8–2 mm; leaves conspicuously hispid. 13 D. hengduanensis

+ Spikelets 1.3–1.7 mm; leaves glabrous to pilose (17)

17 (16) Racemes 2–5, 3–8 cm; culms 30–90 cm; spikelets pubescent; apex of fertile floret protruding above lower lemma. 14 D. abludens

+ Racemes 5–8, 10–17 cm; culms 80–110 cm; spikelets coarsely villous; apex of fertile floret not protruding. 15 D. jubata

18 (12) Upper lemma pale yellowish brown or gray at maturity; plant stoloniferous (19)

+ Upper lemma dark brown to blackish purple at maturity; plant usually tufted (20)

19 (18) Spikelets 1.7–2.3 mm; lower lemma with equidistant veins. 16 D. mollicoma

+ Spikelets 1.2–1.5 mm; lower lemma with broader intervein spaces flanking midvein. 17 D. longiflora

20 (18) Spikelets glabrous. 19 D. stewartiana

+ Spikelets pilose (21)

21 (20) Racemes 2–4, divaricate; spikelets elliptic, 2–2.2 mm. 20 D. ischaemum

+ Racemes (2–)3–10, ascending; spikelets elliptic-oblong, 1.2–1.9 mm (22)

22 (21) Upper glume 1/4–1/2 spikelet length. 22 D. fauriei

+ Upper glume subequaling spikelet (23)

23 (22) Rachis 0.5–0.8 mm broad; spikelets 1.4–1.9 mm. 21 D. violascens

+ Rachis 0.3–0.5 mm broad; spikelets 1.2–1.5 mm. 18 D. leptalea

List of lower taxa

Related Objects

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