Horkelia tenuiloba
Horkelia yadonii
Santa Rosa, Santa Rosa horkelia, Sonoma horkelia, thin-lobed, thin-lobed horkelia
Santa Lucia horkelia, Yadon's or Santa Lucia horkelia
ascending to erect, 1–4 dm, hairs ± spreading.
ascending to erect, (0.5–)2–6(–7) dm, hairs spreading.
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.
± planar, (3–)6–20(–32) × 0.5–1.5(–2) cm;
stipules entire;
leaflets 7–16 per side, separate to ± overlapping especially distally, broadly cuneate to nearly round, (3–)4–15(–17) × (2–)5–12 mm, 3/4 to nearly as wide as long, divided 1/5–1/2 to midrib into (3–)8–15(–30) acute to obtuse teeth, often medially notched as well 1/3–2/3 to midrib, villous.
2–5.
3–5.
open to congested, flowers arranged individually and in glomerules, these sometimes subcapitate.
open, flowers arranged individually and in glomerules.
1–6 mm.
1–7(–20) mm.
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.
8–12 mm diam.;
epicalyx bractlets lanceolate to ovate, 1.5–4.5 × 1–2(–2.5) mm, 1/2–3/4 length of sepals, entire;
hypanthium 1.5–3 × 3–6.5 mm, less than 1/2 as deep as wide, interior sparsely pilose;
sepals spreading to ± reflexed, lanceolate, (3–)4–6.5 mm;
petals broadly oblanceolate-elliptic, 3–5.5 × 2–3 mm, apex truncate;
filaments 1–2 × 0.5–1 mm, anthers 0.8–1.2 mm;
carpels 20–60;
styles 2.5–3 mm.
light brown, 1.5 mm, smooth or slightly rugose.
brown, 1.5 mm, smooth.
= 28.
Horkelia tenuiloba
Horkelia yadonii
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.
Horkelia yadonii is known only from localized populations in the La Panza, San Rafael, and Santa Lucia ranges of Monterey, San Luis Obispo, and Santa Barbara counties. The isolated populations often differ in such characters as general size, leaf proportions, and shape of epicalyx bractlets. The most distinctive extreme, in Monterey County, is characterized by relatively long, narrow leaves, small, few-toothed leaflets, long pedicels, few small flowers, and ovate bractlets. These differences, however, are not consistently or sharply defined.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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