Horkelia sect. Horkelia
Horkelia bolanderi
Bolander's horkelia, border horkelia
decumbent or ascending to erect, (0.5–)1–10(–12) dm.
ascending to erect, 1–3(–4.5) dm, hairs ascending to appressed.
usually planar, sometimes ± cylindric;
stipules usually entire, sometimes basally lobed;
leaflets (1–)3–16(–20) per side, separate to overlapping, divided ± 1/6–3/4+ to midrib into 3–30(–60) teeth or lobes not restricted to apex.
± planar, 3–8(–9) × 0.7–1.5 cm;
stipules entire;
leaflets 6–9 per side, separate to ± overlapping at least distally, ± cuneate to obovate, 4–10 × 2–7 mm, 1/2 to nearly as wide as long, divided 1/3 to midrib into 3–6 acute, sometimes obtuse, teeth, densely strigulose, often villous marginally or at least apically.
(2 or)3–6.
open to congested, flowers arranged individually, in usually non-capitate glomerules, and/or in corymbiform clusters.
± congested to open, most flowers arranged in glomerules.
remaining straight, 1–30(–40) mm.
(1–)2–4(–6) mm.
epicalyx bractlets narrowly elliptic-lanceolate to broadly ovate, 0.5–3 mm wide, usually entire, sometimes toothed;
hypanthium interior pilose or glabrous;
sepals acute;
petals white, oblong-oblanceolate to round, apex obtuse to truncate to emarginate;
filaments white, glabrous, anthers longer than wide;
carpels 10–200(–220).
10 mm diam.;
epicalyx bractlets elliptic-lanceolate, (1.5–)1.8–3 × 0.5–1 mm, ± 2/3 length of sepals, entire;
hypanthium 1–1.5 × 2–4 mm, less than 1/2 as deep as wide, interior slightly pilose;
sepals spreading to ± reflexed, lanceolate, (2.5–)3–4 mm;
petals oblong to oblanceolate, 3–5.5 × 1.5–2 mm, apex rounded to slightly emarginate;
filaments 0.5–2 × 0.3–0.4 mm, anthers (0.4–)0.5–0.8 mm;
carpels 10–20(–27);
styles (1–)1.5–2 mm.
0.8–2 mm, usually smooth or slightly rugose, sometimes merely roughened.
brown to dark brown, 1–1.3 mm, usually faintly roughened.
Horkelia sect. Horkelia
Horkelia bolanderi
Species 9 (9 in the flora).
Section Horkelia encompasses the species that are most commonly encountered in heavily populated areas of California. Plants are notably glandular-viscid (unless obscured by dense vestiture) and have a distinctive resinous odor.
Previous revisions (for example, P. A. Rydberg 1908c; D. D. Keck 1938) have placed Horkelia frondosa (here treated as H. californica var. frondosa) at the beginning, implying that this is the least derived expression within the genus. Such an assumption is based on its gross resemblance to sympatric members of Drymocallis; molecular evidence (T. Eriksson et al. 1998; M. Lundberg et al. 2009; C. Dobeš and J. Paule 2010) confirms that this similarity is superficial. If, as speculated above, species composing sect. Hispidulae are relicts of the original radiation, then H. californica var. frondosa is actually one of the more derived members of the genus. Species within sect. Horkelia have been ordered here according to that interpretation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of conservation concern.
W. L. Jepson ([1923–1925]) and P. A. Munz and I. M. Johnston (1925) independently adopted an expanded circumscription of Potentilla bolanderi that included four species of Horkelia recognized by P. A. Rydberg (1908c): H. bernardina, H. bolanderi, H. clevelandii, and H. rydbergii. These were treated as three varieties, which D. D. Keck (1938) converted to subspecies as H. bolanderi subsp. bolanderi, subsp. clevelandii, and subsp. parryi, the last encompassing H. bernardina and H. rydbergii. These subspecies were restored to species rank by B. Ertter (1993c) as H. bolanderi, H. clevelandii, and H. rydbergii, along with the establishment of H. yadonii to accommodate populations from Monterey County assigned to subsp. parryi by Keck.
As now circumscribed, Horkelia bolanderi is known from five locations in the northern Coast Ranges in Colusa, Lake, and Mendocino counties; records from more southerly localities would be referenced to one of the segregate species discussed above.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaflets 1–3 per side, sparsely short-pilose to glabrate, (15–)20–30-toothed 1/6–1/4 to midrib; petals obovate to round, (3–)4–7 mm wide. | H. truncata |
1. Leaflets (3–)5–16(–20) per side, hairy, 3–15(–30)-toothed or -lobed (collectively 10–60-toothed in H. californica) 1/6–3/4+ to midrib; petals narrowly obovate or oblanceolate to elliptic or oblong, 1–3(–4) mm wide | → 2 |
2. Hypanthia 3–5.5 mm, 1/2 to nearly as deep as wide; epicalyx bractlets 4–6(–8) mm, ± equal to sepals, entire or toothed. | H. californica |
2. Hypanthia 1–2(–3) mm, less than 1/2 as deep as wide (except H. clevelandii); epicalyx bractlets 1–4(–5) mm, shorter than sepals, entire | → 3 |
3. Leaflets ± elliptic to obovate, divided less than 1/3 to midrib into (5–)10–15 teeth; epicalyx bractlets 1.5–3 mm wide. | H. cuneata |
3. Leaflets cuneate or flabellate to ovate or nearly round, divided (1/5–)1/3–3/4+ to midrib into 3–10(–30 in H. yadonii) teeth or lobes; epicalyx bractlets 0.5–2(–2.5) mm wide | → 4 |
4. Stems ± decumbent to ascending, 1–3.5(–4.5) dm; leaflets 5–10(–12) per side, cuneate, ± overlapping; inflorescences usually congested; plants matted; coastal. | H. marinensis |
4. Stems ascending to erect, (0.5–)1–7 dm; leaflets 6–16(–20) per side, cuneate to flabellate or nearly round, separate to ± overlapping; inflorescences open to ± congested; plants tufted to matted; coastal or interior | → 5 |
5. Epicalyx bractlets 1–2(–2.5) mm wide, lanceolate to ovate; anthers 0.8–1.2 mm; hypanthia 3–6.5 mm diam. | H. yadonii |
5. Epicalyx bractlets 0.5–1(–1.5) mm wide, narrowly elliptic to broadly lanceolate; anthers 0.4–1 mm; hypanthia 2–4.5(–6) mm diam | → 6 |
6. Stems: hairs ascending to appressed; plants usually grayish to grayish green; hypanthium interior pilose | → 7 |
6. Stems: hairs ± spreading; plants green to grayish; hypanthium interior glabrous or pilose | → 8 |
7. Carpels 20–50(–120); styles 2–4 mm; basal leaves (4–)8–20(–30) cm; Transverse Ranges, s California. | H. rydbergii |
7. Carpels 10–20(–27); styles (1–)1.5–2 mm; basal leaves 3–8(–9) cm; Coast Ranges, n California. | H. bolanderi |
8. Leaflets divided 1/2–3/4+ to midrib into linear to narrowly oblanceolate or narrowly elliptic lobes; hypanthium interior pilose; n Coast Ranges, California. | H. tenuiloba |
8. Leaflets divided 1/3 to midrib into acute to obtuse teeth; hypanthium interior glabrous; Peninsular Ranges, s California. | H. clevelandii |
CA
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