9d. IVESIA Torrey & A. Gray sect. COMARELLA (Rydberg) Ertter & Reveal, Novon. 17: 316. 2007.
Comarella Rydberg, Monogr. N. Amer. Potentilleae, 156, plates 96, 97, figs. 1–5. 1898
Plants usually ± tufted, not forming hanging clumps, not aromatic; taproot stout, not fusiform or fleshy. Stems (1.8–)2–6(–6.5) dm. Basal leaves cylindric; stipules usually present, sometimes much-reduced; leaflets loosely to ± tightly overlapping, individually distinguishable at least distally, toothed 1/3–1/2 or lobed to base, sometimes entire, sparsely to ± densely hairy, sometimes glabrate; terminal leaflets indistinct. Cauline leaves 1–3, not paired; blade well developed. Inflorescences open, flowers arranged individually. Pedicels remaining straight. Flowers: hypanthium patelliform; petals medially reflexed, yellow or red, not clawed, apex acute to obtuse; stamens 5, anthers longer than wide, laterally dehiscent; carpels 1–5. Achenes horizontal, smooth, not carunculate.
Species 2 (2 in the flora): sw United States.
Rydberg established sect. Comarella to accommodate two species with wheel-shaped centrally turbinate hypanthia, linear petals, five stamens, and few carpels that are nearly horizontal at maturity. He understood both species to have purple petals, but the petals of Ivesia sabulosa are actually bright yellow. Other than flower color and leaflet lobing, the two species are nearly identical, with diffuse inflorescences on erect stems emerging from tufts of erect, slender leaves with numerous pairs of leaflets. The medially reflexed petals are unique to these two species of Ivesia, though not always well developed. The stipules of the basal leaves are often little more than slightly rounded, winglike extensions of the petiole base, if they are present at all.
Comarella is the only section of the genus without representation in California. The plants occur at the southeastern corner of the range of Ivesia in the southern Great Basin, southwestern Colorado Plateau, and adjacent Mojave Desert. The Grand Canyon of the Colorado River divides the range of the two species in northern Arizona.