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FNA | Family List | FNA Vol. 9 | Rosaceae | Potentilla

8h. Potentilla Linnaeus sect. Terminales (Döll) Grenier in J. C. M. Grenier and D. A. Godron, Fl. France. 1: 522, 532. 1848–1849.

Barbara Ertter, James L. Reveal

Potentilla [unranked] Terminales Döll, Rhein. Fl., 772. 1843; Potentilla [unranked] Argenteae Rydberg; Potentilla sect. Argenteae (Rydberg) Juzepczuk

Perennials, rosetted or tufted, not stoloniferous; taproots not fleshy-thickened; vestiture of long, short-crisped, and cottony or crisped-cottony hairs, glands absent or sparse to common, not red. Stems decumbent to erect, not flagelliform, not rooting at nodes, from centers of ephemeral basal rosettes, 1–6 dm, lengths (2–)3–5(–10) times basal ˂or proximal cauline˃ leaves. Leaves: basal not in ranks; cauline 2–9; primary leaves usually palmate, sometimes ternate, proximal ones 2–14 cm; petiole: long hairs loosely appressed to spreading, soft to weak, glands absent or sparse to common; leaflets 5–7, at tip of leaf axis, ± overlapping or not, oblanceolate to obovate, margins flat or revolute, distal 1/2–3/4+ evenly to unevenly incised 1/3–3/4+ to midvein, teeth 2–10 per side, surfaces similar to strongly dissimilar, abaxial green to white, cottony and/or crisped hairs absent or sparse to dense, adaxial green, not glaucous, long hairs weak to stiff. Inflorescences 10–100+-flowered, cymose, ± open. Pedicels usually straight in fruit, 0.3–1.5(–3) cm, proximal ± longer than distal. Flowers 5-merous; hypanthium 2–5 mm diam.; petals yellow, obovate to cuneate-obcordate, (2–)2.5–7(–8) mm, slightly shorter to ± longer than sepals, apex rounded to truncate or retuse; stamens ca. 20; styles subapical, columnar-tapered, scarcely to strongly papillate-swollen in proximal 1/5–1/2, 0.6–1.2 mm. Achenes smooth to rugose.

Species 20–30 (3 in the flora): introduced; Eurasia; also introduced in Pacific Islands (New Zealand).

As summarized by A. Kurtto et al. (in J. Jalas et al. 1972+, vol. 13), the species comprising sect. Terminales (including sect. Argenteae) consist of both sexual and apomictic populations of various ploidy levels that can be subdivided into more or less consistent species. The three species adventive in North America are relatively distinct, representing only a subset of European variation. Collections of Potentilla inclinata and P. intermedia are sometimes confused; the former often has petals smaller than the European average, and anthers are often intermediate in size. The distribution of the two species in North America may need adjusting from what is presented here.

Another species complex, the Potentilla collina Wibel group (as addressed by A. Kurtto et al. in J. Jalas et al. 1972+, vol. 13), may be present in North America, at least as an occasional waif. The specimens underlying the citation of this species by P. A. Rydberg (1898, 1908d) are here identified as P. argentea (New York) and P. inclinata (Minnesota); however, variation of traits distinguishing members of sect. Terminales can be subtle and difficult to interpret out of their European context.

Potentilla intermedia is considered to be of hybrid origin involving P. argentea and P. norvegica; it appears to reproduce by both sexual and apomictic means. Some authors consider P. inclinata to be the hybrid derivative of P. argentea and P. recta (A. Kurtto et al. in J. Jalas et al. 1972+, vol. 13). The P. collina group is likewise thought to have a hybrid origin, involving members of sections Aureae and Terminales. Placement of these species in sect. Terminales is made on the basis of key morphologic characters.

1 Leaflet surfaces strongly dissimilar, abaxial white, cottony hairs dense, distal 1/2–2/3 of margin incised 1/2–3/4+ to midvein, teeth 2–3 per side (more if lobed or secondarily toothed).   15 Potentilla argentea
+ Leaflet surfaces similar or ± dissimilar, abaxial green, grayish, or gray-green, cottony hairs absent, distal (1/2–)3/4+ of margin incised 1/3–2/3 to midvein, teeth 4–10 per side   (2)
2 (1) Anthers (0.5–)0.8–1.2 mm; petals 4–7(–8) mm; leaflets grayish to gray-green abaxially, short or crisped hairs usually ± abundant, sometimes sparse, margins usually evenly incised; epicalyx bractlets: lengths ± 1 times sepals.   16 Potentilla inclinata
+ Anthers 0.3–0.5 mm; petals 3–5 mm; leaflets green to grayish green abaxially, short or crisped hairs ± sparse, margins usually unevenly, sometimes evenly, incised (often with 1–2 incisions nearly to midvein); epicalyx bractlets: lengths usually 2/3, sometimes 1, times sepals.   17 Potentilla intermedia


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