8q. Potentilla Linnaeus sect. Brevifoliae (Rydberg) O. Stevens in N. L. Britton et al., N. Amer. Fl. 22(7): 11. 1959.
Barbara Ertter, James L. Reveal
Potentilla [unranked] Brevifoliae Rydberg, Monogr. N. Amer. Potentilleae, 30. 1898
Perennials, tufted to openly matted, not stoloniferous; taproots not fleshy-thickened; vestiture of sparse long hairs, or eglandular hairs absent, glands common to abundant, red. Stems ± erect, not flagelliform, not rooting at nodes, arising laterally to persistent basal rosettes, (0.2–)0.5–1.5(–2.5) dm, lengths 1.5–3(–4) times basal leaves. Leaves: basal not in ranks; cauline 0–2; primary leaves ± pinnate to subpinnate (distal leaflets ± distinct), rarely ternate, 2–7 cm; petiole: long hairs absent or spreading, weak, glands common to abundant; leaflets (3–)5–7, on distal 1/4 or less of leaf axis, usually overlapping, ± flabellate, margins flat, ± whole length unevenly incised 1/2 to nearly to midvein into 3+ lobes ˂these in turn incised 1/4–1/2 to midvein˃, primary teeth of each lobe usually 2–3, often secondarily toothed, surfaces similar, green, not glaucous, long hairs (if present) weak, cottony hairs absent. Inflorescences (1–)3–10-flowered, ± cymose, open, or solitary flowers. Pedicels straight in fruit, 0.1–1 cm, proximal not much longer than distal. Flowers 5-merous; hypanthium 2.5–4.5 mm diam.; petals yellow, ± obcordate, 3.5–6.5 mm, longer than sepals, apex retuse; stamens ca. 20; styles subapical, filiform, ± papillate-swollen at very base, if at all, 1.4–2 mm. Achenes smooth.
Species 3 (1 in the flora): nw United States, n Mexico.
Section Brevifoliae is primarily based on Potentilla brevifolia, distinctive in its abundant short-septate glands and the three to seven overlapping, more or less flabellate leaflets, most often in a subpinnate arrangement. Two Mexican species, P. macdonaldii B. L. Turner and P. richardii Lehmann, are included provisionally in the section. The rounded membranous stipules suggest a close relationship with sect. Aureae, especially P. cristae, which is also abundantly glandular.