Horkelia sericata |
Rosaceae tribe Potentilleae |
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Howell's horkelia, silky horkelia |
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Habit | Plants ± tufted, silvery. | Herbs, perennial, rarely annual or biennial, shrubs, or subshrubs; unarmed. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | ascending to erect, 1.5–4.5 dm, hairs 1 mm proximally, glands absent or sparse distally. |
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Leaves | alternate, rarely opposite, pinnately (palmately) compound (simple in Alchemilla, Aphanes, and Chamaerhodos); stipules persistent (absent in Chamaerhodos), adnate to petiole; venation pinnate or palmate. |
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Basal leaves | ± 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. |
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Cauline leaves | (2 or)3–5; stipules 3–8 mm, entire or shallowly 1–2-toothed. |
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Inflorescences | open, flowers arranged individually and/or in non-capitate glomerules. |
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Pedicels | 1–4 mm. |
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Flowers | 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. |
perianth and androecium perigynous; epicalyx bractlets present, sometimes absent; hypanthium usually patelliform, cupulate, or campanulate, sometimes turbinate, saucer-shaped, flat-bottomed, or subglobose to ellipsoid or ovoid; torus flat to conic or turbinate, enlarged (absent or reduced in Alchemilla, Aphanes, and Chamaerhodos); carpels 1–260, styles basal or lateral to subterminal, distinct; ovules 1(or 2), basal. |
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Fruits | aggregated achenes (achenes in Alchemilla and Aphanes); torus sometimes fleshy; styles deciduous or persistent, not elongate. |
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Achenes | brown, 2–2.5 mm, smooth. |
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2n | = 28. |
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Horkelia sericata |
Rosaceae tribe Potentilleae |
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Phenology | Flowering summer. | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Chaparral, oak-conifer woodlands, on serpentine-derived soil | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 100–1200 m (300–3900 ft) | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
CA; OR
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North America; Mexico; Central America; South America; West Indies; Bermuda; Eurasia; Africa; Atlantic Islands; Pacific Islands; Australia |
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Discussion | 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.) |
Genera 14–22, species ca. 860 (14 genera, 189 species, including 1 hybrid, in the flora area). The base chromosome number for Potentilleae is mostly x = 7 (8 in Alchemilla and Aphanes; 14 in Comarum). Variation in the number of genera recognized in Potentilleae is due to differences in generic delimitation between D. Potter et al. (2007) and the authors of Potentilla and segregates here (see 9. Ivesia and 8. Potentilla for discussion). In the former, Duchesnea, Horkelia, Horkeliella, and Ivesia are included within Potentilla. Likewise, Aphanes is included within Alchemilla by Potter et al. while it is kept distinct here. Potentilla and its segregates and Fragaria are host to Phragmidium rusts, but not the other genera of the tribe. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 9, p. 265. | FNA vol. 9, p. 119. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae | Rosaceae > subfam. Rosoideae | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | Potentilla sericata | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | S. Watson: Proc. Amer. Acad. Arts 20: 364. (1885) | Sweet: Brit. Fl. Gard. 2: sub plate 124. (1825) | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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