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

9c. IVESIA Torrey & A. Gray sect. UNGUICULATAE (Rydberg) O. Stevens in N. L. Britton et al., N. Amer. Fl. 22(7): 8. 1959.

Horkelia Chamisso & Schlechtendal [unranked] Unguiculatae Rydberg, Monogr. N. Amer. Potentilleae, 124. 1898; Horkelia [unranked] Eremicae Rydberg; Ivesia [unranked] Eremicae (Rydberg) Rydberg; Ivesia sect. Eremicae (Rydberg) O. Stevens; Ivesia [unranked] Unguiculatae (Rydberg) Rydberg

Plants usually rosetted or tufted, rarely ± matted (I. kingii var. eremica), not forming hanging clumps, not aromatic; taproot stout to fusiform and fleshy. Stems (0.3–)1–4.5(–5.5) dm. Basal leaves loosely to tightly cylindric (± mousetail-like in I. argyrocoma and I. kingii var. eremica); stipules present or absent; leaflets loosely or, sometimes, tightly overlapping, individually distinguishable or not, lobed to base, sometimes entire; terminal leaflets indistinct, sparsely to densely hairy or glabrate. Cauline leaves (1–)2–10(–15), not paired; blade ± well developed. Inflorescences open to congested, flowers arranged individually and/or in glomerules, these usually ± capitate. Pedicels remaining ± straight (rarely ± curved in I. argyrocoma). Flowers: hypanthium shallowly cupulate or campanulate to turbinate, rarely patelliform (I. pityocharis); petals not medially reflexed, light yellow to white, sometimes pink-tinged, ± clawed, apices rounded or truncate to emarginate; stamens usually 20 (10–15 in I. unguiculata, 12–20 in I. campestris), anthers ± as long as to longer than wide, laterally dehiscent; carpels (1–)2–20. Achenes vertical, smooth, not carunculate.

Species 8 (8 in the flora): w United States, nw Mexico.

Section Unguiculatae encompasses a series of species that have radiated in montane meadows in California, from Siskiyou and Trinity counties through the Sierra Nevada to the San Bernardino Mountains, and in the Carson, Virginia, and Pine Nut ranges in adjacent Nevada; one variety of Ivesia argyrocoma is endemic to the Sierra San Pedro Mártir in Baja California, Mexico. The species occur in seasonally wet/dry meadows and flats, including some specific substrate types of localized occurrence that often support suites of endemic species. The most widespread species in the section, I. kingii, has adapted to alkali-crusted valley bottoms extending across the Great Basin to western Utah.

Members of sect. Unguiculatae are nearly glabrous to densely sericeous but lack the conspicuous glandularity and distinctive ivesioid smell that characterize sects. Ivesia and Setosae. The taproot is often elongate and fleshy-thickened, which is apparently an adaption for when the preferred habitat becomes seasonally desiccated. Leaves are cylindric with deeply lobed leaflets. Flowers are usually aggregated into multiple few- to many-flowered glomerules; sometimes they are individually arranged in diffuse inflorescences. Petals are white to pale yellow but never golden yellow and are often conspicuously clawed. Stamens are commonly 20 except in Ivesia campestris and I. unguiculata.

1 Filaments flattened; leaflets (1–)2–3.5 mm, tightly overlapping; plants silvery; stems prostrate to ascending, (0.3–)1–2.5(–3) dm; cauline leaves (1–)2–3; San Bernardino Mountains, s California.   27 Ivesia argyrocoma
+ Filaments filiform; leaflets (1.5–)2–15(–20) mm, loosely overlapping (tightly so in some I. kingii); plants green to grayish or silvery; stems prostrate-decumbent to erect, (0.5–)1–4(–5.5) dm; cauline leaves 2–15; w United States   (2)
2 (1) Stamens 10–20, filaments 0.6–1.1 mm; leaflets 15–20(–25) per side; c, s Sierra Nevada, California   (3)
+ Stamens 20, filaments (1–)1.5–4 mm; leaflets 15–50(–60) per side; n California to Utah   (4)
3 (2) Petals 5, white, often tinged with pink; sepals heavily purple-mottled; inflorescences (15–)30–100(–200)-flowered; c Sierra Nevada.   25 Ivesia unguiculata
+ Petals 4(–5), light yellow; sepals green; inflorescences 5–20(–40)-flowered; s Sierra Nevada.   26 Ivesia campestris
4 (2) Flowers arranged in tight glomerules of 5–20 flowers; pedicels 1–3(–15) mm   (5)
+ Flowers arranged individually or in loose glomerules of 2–10 flowers; pedicels (1–)2–20(–25) mm   (6)
5 (4) Petals white; petiole hairs usually spreading, 1–4 mm; hypanthia campanulate to shallowly turbinate, 1.5–3 mm, often nearly as deep as wide.   22 Ivesia sericoleuca
+ Petals light yellow; petiole hairs ascending, ± 1(–3) mm; hypanthia cupulate, 1–2 mm, 1/2–2/3 as deep as wide.   23 Ivesia aperta
6 (4) Petals oblanceolate to narrowly spatulate; hypanthia cupulate to turbinate, 1.5–3 mm, often nearly as deep as wide; on ultramafic-derived soil; n California.   21 Ivesia pickeringii
+ Petals spatulate or obovate to orbiculate; hypanthia shallowly cupulate to patelliform, 0.5–2.5 mm, ± 1/2 as deep as wide; on alkaline soil or in non-alkaline meadows; Great Basin and n Mojave Desert   (7)
7 (6) Leaflets 15–60 per side, hairs absent or 0.2–0.5(–1) mm, ± appressed; carpels 2–9; alkali-crusted flats, e California, Nevada, sw Utah.   20 Ivesia kingii
+ Leaflets 5–25 per side, hairs 1–3 mm, spreading to ascending; carpels 8–20; meadows in sagebrush, Pine Nut Mountains, Nevada.   24 Ivesia pityocharis


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