Flora of North America species comparison

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Horkelia sericata

Howell's horkelia, silky horkelia
Habit Plants ± tufted, silvery.
Stems

ascending to erect, 1.5–4.5 dm, hairs 1 mm proximally, glands absent or sparse distally.
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.
Cauline leaves

(2 or)3–5;

stipules 3–8 mm, entire or shallowly 1–2-toothed.
Inflorescences

open, flowers arranged individually and/or in non-capitate glomerules.
Pedicels

1–4 mm.
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.
Achenes

brown, 2–2.5 mm, smooth.
2n

= 28.

Horkelia sericata
Phenology Flowering summer.
Habitat Chaparral, oak-conifer woodlands, on serpentine-derived soil
Elevation 100–1200 m (300–3900 ft)
Distribution
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
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.)
Source FNA vol. 9, p. 265.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae
Sibling taxa
H. bolanderi, H. californica, H. clevelandii, H. congesta, H. cuneata, H. daucifolia, H. fusca, H. hendersonii, H. hispidula, H. howellii, H. marinensis, H. parryi, H. rydbergii, H. tenuiloba, H. tridentata, H. truncata, H. tularensis, H. wilderae, H. yadonii
Synonyms Potentilla sericata
Name authority S. Watson: Proc. Amer. Acad. Arts 20: 364. (1885)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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