Ivesia sect. Stellariopsis
Novon 17: 317. 2007.
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.
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.
"dm" is not declared as a valid unit of measurement for this property.