Horkelia tenuiloba |
Horkelia sericata |
|
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Santa Rosa, Santa Rosa horkelia, Sonoma horkelia, thin-lobed, thin-lobed horkelia |
Howell's horkelia, silky horkelia |
|
Habit | Plants loosely matted, green. | Plants ± tufted, silvery. |
Stems | ascending to erect, 1–4 dm, hairs ± spreading. |
ascending to erect, 1.5–4.5 dm, hairs 1 mm proximally, glands absent or sparse distally. |
Basal leaves | weakly planar to ± cylindric, 5–15(–20) × 0.5–1.5 cm; stipules entire; leaflets 8–16(–20) per side, ± overlapping especially distally, cuneate to flabellate, 3–10 × 2–10 mm, 1/2 to nearly as wide as long, divided 1/2–3/4+ to midrib into 3–8 linear to narrowly oblanceolate or narrowly elliptic lobes, sparsely villous at least marginally, often with a tuft of hairs apically. |
± cylindric to weakly planar, 3–10 × 0.3–1.2 cm, densely sericeous, often villous on margins apically; stipules usually entire or forked, rarely pinnately divided into linear lobes; leaflets (8–)10–20 per side, ± overlapping, elliptic to flabellate, 2–8 × 1–4 mm, 1/2–2/3 as wide as long, divided ± 1/2+ to midrib into (0–)2–4 elliptic lobes 1–2 mm wide, these not restricted to apex. |
Cauline leaves | 2–5. |
(2 or)3–5; stipules 3–8 mm, entire or shallowly 1–2-toothed. |
Inflorescences | open to congested, flowers arranged individually and in glomerules, these sometimes subcapitate. |
open, flowers arranged individually and/or in non-capitate glomerules. |
Pedicels | 1–6 mm. |
1–4 mm. |
Flowers | 10 mm diam.; epicalyx bractlets narrowly to broadly lanceolate, 1–3 × 0.5–1 mm, slightly shorter than sepals, entire; hypanthium 1–1.2 × 2.5–4.5 mm, less than 1/2 as deep as wide, interior pilose; sepals spreading to reflexed, lanceolate, 3–5 mm; petals oblanceolate, 2.5–4.5 × 1.5 mm, apex emarginate; filaments (1–)1.5–2 × 0.5 mm, anthers 0.4–0.6 mm; carpels 10–25; styles 1.8–2.2 mm. |
10 mm diam.; epicalyx bractlets linear-lanceolate, 1.5–3 × 0.5 mm, ± 2/3 length of sepals; hypanthium 1–1.5 × 2–3 mm, ± 1/2 to as deep as wide, interior glabrous; sepals spreading to reflexed, abaxially green to reddish or purplish, 2–4 mm; petals white to pink or red-veined, narrowly obcordate, 3–4.5(–7) × 2–3 mm, apex ± emarginate; filaments 0.5–1.5 × 0.2–0.5 mm, anthers 0.4–0.6 mm; carpels 2–6; styles 1.5–2 mm. |
Achenes | light brown, 1.5 mm, smooth or slightly rugose. |
brown, 2–2.5 mm, smooth. |
2n | = 28. |
= 28. |
Horkelia tenuiloba |
Horkelia sericata |
|
Phenology | Flowering summer. | Flowering summer. |
Habitat | Sandy soil, openings, in chaparral, oak woodlands | Chaparral, oak-conifer woodlands, on serpentine-derived soil |
Elevation | 50–500 m (200–1600 ft) | 100–1200 m (300–3900 ft) |
Distribution |
CA
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CA; OR
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Discussion | Of conservation concern. Horkelia tenuiloba occurs on the western edges of the northern Coast Ranges in Marin, Mendocino, and Sonoma counties. Populations from San Luis Obispo formerly included in this species now are part of H. yadonii. A specimen (M. K. C[urran], July 5, 1885, UC) unequivocally of H. tenuiloba purportedly from San Luis Obispo is in all likelihood mislabeled with respect to locality. Horkelia tenuiloba is commonly associated with seral openings in chaparral and woodlands and might be dependent on periodic disturbance by fire. W. L. Jepson (1909–1943, vol. 2) used Potentilla stenoloba (1895) for the species encompassing the types of Horkelia tenuiloba and P. micheneri. The epithet micheneri (1893) has priority at species rank within Potentilla, since P. tenuiloba (Torrey) Greene is a later homonym of P. tenuiloba Jordan. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. D. D. Keck (1938) expanded the circumscription of Horkelia sericata to encompass the plants segregated here as H. howellii, on the grounds that intergradation is too extensive to justify taxonomic recognition of the extremes. In this evaluation, however, most collections can be unequivocally divided between plants with compact silvery-sericeous leaves with entire or forked stipules (H. sericata), and plants with larger, greener leaves and pinnately divided stipules (H. howellii). It is not known if the chromosome count provided by P. A. Munz (1959) was derived from H. howellii or H. sericata. As here circumscribed, Horkelia sericata is a localized taxon known only from Curry County, Oregon, and the Gasquet serpentine area in adjacent Del Norte County, California. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 9, p. 252. | FNA vol. 9, p. 265. |
Parent taxa | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Horkelia | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae |
Sibling taxa | ||
Synonyms | H. fusca var. tenuiloba, Potentilla micheneri, P. stenoloba | Potentilla sericata |
Name authority | (Torrey) A. Gray: Proc. Amer. Acad. Arts 6: 529. (1865) | S. Watson: Proc. Amer. Acad. Arts 20: 364. (1885) |
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