8a. Potentilla Linnaeus sect. Pentaphylloides Tausch, Hort. Canal. sub P. ornithopoda. 1823.
Reidar Elven, David F. Murray
Argentina Hill; Potentilla sect. Anserina (Gaudin) Pfeiffer; Potentilla ser. Anserina (Gaudin) T. T. Yu & C. L. Li; Potentilla subg. Argentina (Hill) Jepson
Perennials, openly matted, stoloniferous [to ± tufted, not stoloniferous]; taproots not fleshy-thickened, ˂often absent and replaced by ± thickened lateral roots˃; vestiture primarily of long and crisped-cottony hairs, glands absent or sparse, not red. Stems prostrate [to erect], flagelliform [or not], rooting at nodes [or not], lateral to ± persistent basal rosettes, 1–10+ dm, lengths (0.5–)1–5+ times basal leaves. Leaves: basal not or ± 2-ranked; cauline (between flowering and/or rosette-forming nodes) 0–1; primary leaves pinnate (distal leaflets sometimes confluent), (1–)3–50(–75) cm; petiole: long hairs absent or ascending to weakly appressed, sometimes spreading, soft to weak, glands absent or very sparse; primary leaflets (5–)7–21(–31[–51]) plus additional small leaflets interspersed, on distal (1/2–)2/3–4/5+ of leaf axis, overlapping or not, elliptic to obovate, margins revolute or nearly flat, distal (1/2–)2/3–3/4+ evenly incised 1/4–1/2 to midvein, teeth (2–)5–12(–16) per side, surfaces similar to strongly dissimilar, abaxial usually white, sometimes green, cottony(/crisped) hairs usually dense, sometimes sparse or absent, adaxial green to white, not glaucous, long hairs absent or weak to soft. Inflorescences solitary flowers ˂at stolon nodes˃ [± cymose]. Pedicels straight in fruit, (1–)2–45(–55) cm. Flowers 5(–7)-merous; hypanthium 3–7 mm diam.; petals bright yellow, elliptic to broadly elliptic, (4–)5–15(–20) mm, longer than sepals, apex rounded or slightly retuse; stamens [5–]20(–30); styles ± lateral [subapical or sub-basal], narrowly columnar-filiform, not papillate-swollen proximally, 1.5–2.5 mm. Achenes slightly rugose and papillate.
Species ca. 50 (1 in the flora): North America, Mexico, South America (Argentina, Chile), Eurasia, Pacific Islands (New Guinea, New Zealand), s Australia.
The use here of sect. Pentaphylloides is contrary to the argument by J. Soják (2007) that the use of Pentaphylloides Tournefort by G. R. Boehmer (in C. G. Ludwig 1760) qualified as an unranked infrageneric taxon, making sect. Pentaphylloides Tausch a later homonym. In that Boehmer was citing synonyms, not infrataxa, sect. Pentaphylloides Tausch is the correct name for this section. The names sect. Chenopotentilla Focke and sect. Leptostylae (Th. Wolf) Guşuleac are superfluous and illegitimate.
Potentilla anserina is the atypical and only representative in North America of a primarily southeastern Asian section. Although provisionally retained within Potentilla, the morphological distinctiveness of the section has led to the recognition of Argentina as a segregate genus (for example, P. A. Rydberg 1908d; Á Löve and D. Löve 1975b; B. C. Johnston 1985; J. Soják 2010). Molecular analyses (C. Dobeš and J. Paule 2010; M. H. Töpel et al. 2011) have confirmed the section is a strongly supported monophyletic clade, albeit including some other Asian species treated by J. Soják (1994) as the segregate genera Piletophyllum (Soják) Soják and Tylosperma Botschantzev. Chloroplast markers (Dobeš and Paule; Töpel et al.) place this clade sister to all other Potentilleae; nuclear markers (Töpel et al.) indicate instead a sister relation to Fragariinae.
SELECTED REFERENCES Rousi, A. 1965. Biosystematic studies on the species aggregate Potentilla anserina L. Ann. Bot. Fenn. 2: 47–112. Soják, J. 2010. Argentina Hill, a genus distinct from Potentilla (Rosaceae). Thaiszia 20: 91–97.