79. Potentilla vulcanicola Juzepczuk, Bot. Mater. Gerb. Bot. Inst. Komarova Akad. Nauk SSSR. 17: 222. 1955.
Plants densely tufted. Caudex branches stout, sometimes ± columnar, not sheathed with marcescent whole leaves. Stems ascending to erect, (0.2–)0.4–1.6(–2) dm, lengths 2–3 times basal leaves. Basal leaves 1–6(–11) cm; petiole 0.5–4(–9) cm, long hairs ± abundant, ascending to spreading, sometimes loosely appressed, 1–2.5 mm, soft to weak, smooth, crisped(/cottony) hairs absent or sparse, sometimes common, glands absent or sparse; leaflets overlapping, central broadly obovate, 0.8–2(–2.5) × 0.8–1.5(–2.5) cm, sessile or subsessile, base broadly cuneate, margins strongly revolute, distal 1/2–2/3 incised ± 1/2 to midvein, teeth 2–3(–4) per side, distant, surfaces strongly dissimilar, abaxial grayish white, long hairs 1–2 mm, cottony-crisped hairs ± dense, adaxial usually dark green, sometimes grayish green, long hairs sparse to abundant, other hairs usually absent. Cauline leaves (0–)1–2(–3). Inflorescences 1–2(–5)-flowered. Pedicels 1–2 cm in flower, to 5 cm in fruit. Flowers: epicalyx bractlets ± oblong to ovate, 4–8(–10) × 1.8–3(–5) mm, 2/3 to as wide as sepals, margins revolute, sometimes flat, red glands absent; hypanthium 3.5–4.5 mm diam.; sepals 5–8 mm, apex ± acute; petals 7–9 × 7–10 mm, longer than sepals; filaments 0.8–1 mm, anthers 0.6–0.7 mm; carpels 20–30, apical hairs sparse to abundant (straight), styles conic-columnar, ± papillate-swollen in less than proximal 1/5, or sometimes to 1/5, 0.8–1.1 mm. Achenes 0.9–1.2 mm. 2n = 28 (Russian Far East).
Flowering late spring to summer. Dry alpine heaths, ridge crests, rock outcrops, herb slopes, scree and talus, stabilized sand dunes, mainly on calcareous bedrock; 0–3100 m; N.W.T., Nunavut, Yukon; Alaska; e Asia (Russian Far East).
Potentilla vulcanicola is close morphologically to P. uniflora in the narrow sense and largely replaces it in southern and eastern Chukotka, Alaska, and northwestern Canada, where it reaches east of Mackenzie River on the coastal mainland and the westernmost islands (Banks and Victoria islands). Potentilla subgorodkovii and P. vulcanicola account for a major part of North American records of P. uniflora.