Microstegium tenue (Trin.) Hosok.

Chen, H., Veldkamp, J. - F. & Kuoh, C. - S., 2012, Taxonomic revision of Microstegium s. str. Andropogoneae, Poaceae), Blumea 57 (2), pp. 160-189 : 182

15. Microstegium tenue (Trin.) Hosok. — Fig. 13 ; Map 11

Microstegium tenue (Trin.) Hosok. (1938) 150; Jansen (1953) 307, isonym. — Pollinia tenuis Trin. (1832) 306. — Eulalia tenuis Kuntze (1891) 775. — [ Pogonatherum glabratum (Brongn.) Roberty subvar. tenue Roberty (1960) 389, nom. inval.]. — Type: Chamisso 24 in Herb. Trinius 58.1 (LE, microfiche IDC BT-16/1; W).

Pleuroplitis producta Griseb.(1853) 478. — Andropogon productus (Griseb.) Regel (1866) 760, t. 2, f. 16–21. — Type: Eschscholtz s.n. (holo LE, L. film 35, neg. 23).

Annuals, mat-forming. Culms rambling, weak, 20–100 cm long, rooting from the lower nodes. Nodes glabrous. Sheaths glabrous, outer margin glabrous, oral hairs absent or ciliate. Ligule a glabrous membrane, c. 1 mm long. Blades linear or lanceolate, 4–20 cm by 4–8 mm, firm, base attenuate to slightly rounded, pseudopetiole absent, margins scabrous, apex acute to acuminate, glabrous to sparsely pilose on both sides, with tubercle-based hairs. Panicles 3–5 cm long, common axis c. 0.5 cm long. Racemes 2–4, digitate, ascending, straight, 2–5 cm long. Rachis fragile, flattened, margins ciliate, internodes pyriform, 1.5–2 mm long. Sessile spikelets without a short stalk, deciduous with the adjacent joint and pedicel, lanceolate, 2–3 mm long, callus puberulous. Lower glume oblong to lanceolate, coriaceous, midrib glabrous, dorsally longitudinally grooved, smooth, glabrous, margins glabrous, apex entire or dentate. Upper glume elliptic, back acute, glabrous, midrib glabrous, apex entire, acute, mucro 1–3 mm long. Lower florets present, well-developed, paleate or barren, epaleate. Lower lemma lanceolate, c. 1.5 mm long, muticous. Upper lemma lanceolate, c. 0.3 mm long, without veins, glabrous, apex entire, awn geniculate, column twisted, 7–12 mm long. Upper palea absent or minute. Anthers 1, c. 0.5 mm long. Pedicels clavate, flattened, c. 1.5 mm long, margins pubescent. Pedicelled spikelets variously reduced.

Distribution — Taiwan, Philippines (Luzon), Micronesia (Kosrae).

Habitat — Dry open slopes, cliffs, 0–1200 m altitude.

Notes — The only specimen in Taiwan was collected in 1960. It is unclear whether this species is still extant there ( Chen et al. 2011b).

The line drawing of this species has been published previously ( Chen et al. 2011b).

Figures

Fig. 13 Microstegium tenue (Trin.) Hosok. a. Habit; b. spikelets; c. lower glume; d. upper glume; e. lower lemma; f. upper lemma with awn; g. upper palea; h. joint of leaf sheath and leaf blade (all: Merrill 4310, P).