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23. Poa arctica R. Brown subsp. caespitans Simmons ex Nannfeldt, Symb. Bot. Upsal. 4: 71. 1940.

极地早熟禾 ji di zao shu he

Poa tolmatchewii Roshevitz.

Perennials, densely tufted, short rhizomatous or not (Chinese plants); shoots extravaginal and some intravaginal. Culms solitary to several (rarely up to 20, Chinese plants), 7.5–60 cm tall, 0.5–2 mm in diam., smooth, glabrous, nodes 1 or 2, none or 1 exserted, uppermost to 1/3 way up, base of culms with sheaths soon withering (in Chinese plants). Leaf sheaths weakly keeled, smooth, glabrous, 2–15 cm, 1.5–5 × as long as blade, uppermost closed for 1/4–1/3 of length; blades flat or folded, papery to thickly papery, 1–6 mm wide, surfaces smooth or sparsely scabrid, of tillers folded, 2–15 cm; ligule 2–4 mm, abaxially smooth or sparsely scabrid, apex obtuse to acute. Panicle open, ovoid to pyramidal, well exserted, 3–10 (–15) × 2–6 cm, internodes 0.8–1.5(–3) cm; branches spreading early, sinuous and flexuous to strict, (1–)2–5 per node, slender to moderately stout, rounded, smooth or distally scabrid, longest 1.5–5 cm with 2–7 spikelets in distal 1/3. Spikelets ovate, strongly purple tinged, 4–5(–5.5) mm, florets (2–)3–4 (–6); vivipary absent (within China); rachilla internodes 0.8–1.2 mm, smooth, glabrous, or short villous (within China); glumes subequal, lanceolate, very thinly papery, 3-veined, weakly keeled, smooth or sparsely scabrid, lower glume (2–)2.5–4.5 mm, upper glume (2.5–)3–5 mm; lemmas lanceolate to broadly lanceolate, 3.5–4.5 mm, margins broadly membranous, apex acute, keel densely long-villous for 3/4 of length, marginal veins to 2/3, intermediate veins prominent, area between veins smooth to moderately bumpy, distally smooth or sparsely scabrid, proximally (sparsely to) densely shortly villous; callus webbed, hairs usually dense, to 1/2 as long as lemma; palea sparsely to moderately pilulose between keels, keels scabrid, medially pilulose. Anthers 1.4–2.5 mm. Fl. and fr. Jul–Aug. 2n = 77.

Wet places along glacial rivers or lakes, alpine meadows, grassy places on rocky slopes; ca. 2100 m. Heilongjiang, Jilin [Russia; Europe (Scandinavia), North America].

The only Chinese material seen by the authors is from Jilin (Changbai Shan), and this is tentatively placed within subsp. caespitans. The specimens have no evident rhizomes, like subsp. caespitans. The rachillas are strongly pilose as in subsp. lanata (Scribner & Merrill) Soreng (incl. Poa malacantha Komarov), but the leaf blades are too thin and the spikelets too small for that taxon. Poa arctica subsp. arctica is distinguished by its loose, rhizomatous habit, mostly solitary culms, and generally glabrous rachillas. These gatherings had been identified as P. shinoana Ohwi (P. malacantha subsp. shinoana (Ohwi) T. Koyama; P. malacantha var. shinoana (Ohwi) Ohwi). FRPS (9(2): 132. 2002) reported P. tolmatchewii from Heilongjiang, but we have not seen a voucher specimen. Specimens named as P. arctica subsp. arctica from Gansu, Hebei, Nei Mongol, Qinghai, and Xinjiang have been redetermined as other species, mostly P. tangii. Poa arctica subsp. arctica is a circumboreal arctic and alpine species, and is known as far south as ca. 50°N in the mountains S of Lake Baikal (but not from Mongolia) and from northernmost Korea (P. deschampsioides Ohwi), but there seems to be little or no suitable habitat in adjacent parts of China.


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