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

9e. IVESIA Torrey & A. Gray sect. STELLARIOPSIS (Baillon) Ertter & Reveal, Novon. 17: 317. 2007.

Potentilla Linnaeus sect. Stellariopsis Baillon, Hist. Pl. 1: 370. 1869; Stellariopsis (Baillon) Rydberg

Plants tufted, not forming hanging clumps, not aromatic; taproot ± stout, not fusiform or fleshy. Stems (1–)1.5–4 dm. Basal leaves very tightly cylindric (mousetail-like); stipules present; leaflets tightly overlapping, individually scarcely distinguishable, lobed to base, sometimes entire, densely hairy; terminal leaflets indistinct. Cauline leaves 1–3, not paired; blade relatively well developed. Inflorescences open, flowers arranged individually. Pedicels remaining ± straight. Flowers: hypanthium shallowly campanulate; petals not medially reflexed, white, short-clawed, apex rounded; stamens 15, anthers shorter than wide, dehiscing by subterminal pores to short lateral slits; carpels 1. Achenes vertical, smooth, not carunculate.

Species 1: California.

P. A. Rydberg (1898) recognized Stellariopsis at the generic level primarily on the basis of the obcordate anthers, which apparently open by terminal pores, as well as the single carpel, mousetail-like leaves, diffuse inflorescence, and flowers intermediate between Ivesia and Potentilla. J. Soják (2008) argued that the anther character alone justifies generic status. Examination of a series of flowers shows that porelike dehiscence is largely a result of the extreme shortness of the anthers relative to width, such that longer-than-average anthers approach a more typical dehiscence mode. The single carpel and mousetail-like leaves are consistent within the taxon, although both are found elsewhere in the genus (albeit not in the same species). The relatively large, maroon-tipped stipitate glands of the inflorescence branches, including the pedicel and hypanthium, are otherwise unknown in Ivesia.


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