19. Poa tangii Hitchcock, Proc. Biol. Soc. Washington. 43: 94. 1930.
唐氏早熟禾 tang shi zao shu he
Poa shansiensis Hitchcock.
Perennials, loosely tufted, sometimes short rhizomatous; shoots mainly extravaginal. Culms erect, sometimes abruptly decumbent at base, few per tuft, 25–50 cm tall, 0.5–1 mm in diam., smooth, nodes 2 or 3, 1 or 2 exserted, uppermost usually 1/3–1/2 way up. Lower leaf sheaths mostly 1.2–1.5 mm wide, with well-spaced moderately raised ribs, thin between the ribs, smooth or scabrid, sometimes hispidulous, lowermost ones not closely overlapping, papery, withering, longest 4–10 cm, smooth, glabrous, 2–4 × as long as blade, uppermost closed for 2/5–3/4 of length; blade flat, papery to thickly papery, 2–4(–10) cm × 1–2(–3) mm, abaxially smooth, adaxially smooth or scabrid, glabrous, margins finely scabrid, of tillers flat or folded, 5–20 cm, generally with only primary veins expressed abaxially (3–5 veins visible including keel); ligule 0.5–1 mm, apex truncate, errose to fimbriate, adaxially smooth or scabrid, collar margins not or weakly flared, smooth or scabrid, glabrous or the lower ones sometimes ciliate. Panicle open, erect or lax, diffuse, exserted, 2–8 × 2–4 cm, longest internodes 1.2–3.5 cm; branches spreading, 2 per node, slender, rounded, smooth, longest 1.5–4 cm with 1–3 spikelets in distal 1/3; flowers female or perfect, sometimes whole inflorescences female. Spikelets ovate, grayish green, 5–8 mm, florets 3–6; vivipary absent; rachilla internodes 0.7–2.5 mm, smooth or sparsely scabrid, glabrous or sparsely pilulose; glumes very thinly papery, surface smooth, keel smooth or sparsely scabrid, apex obtuse to acute, blunt or pointed, lower glume lanceolate, 2.5–3.5 mm, 1/2–3/4 as wide as upper, 1-veined, upper glume 3–5.5 mm, 3-veined; lemmas oblong, very thinly papery, 4–5.5 mm, apex obtuse, veins glabrous or keel loosely villous for 1/2 of length, marginal veins to 1/3, area between veins smooth or distally scabrid, proximally glabrous or laxly pilulose; callus webbed or diffusely hairy, hairs less than 1/2 as long as lemma; palea, smooth or minutely bumpy (or with sparse minute hooks), glabrous between keels, keels sparsely scabrid, sometimes medially pilulose. Anthers 2.5–3.5 mm, or vestigial. Fl. and fr. May–Jul.
* Wet grassy places along forest margins; 1500–3600 m. Gansu, Hebei, Nei Mongol, Qinghai, Shanxi.
Poa tangii is variable in spikelet pubescence, but the variation is not geographically correlated. The species becomes especially difficult to distinguish from P. polycolea in Gansu and Qinghai, except by its smooth, rounded branches and sparsely scabrid palea keels. Compare P. tangii also with P. veresczaginii in P. subg. Ochlopoa.