Horkelia tenuiloba
Horkelia marinensis
Santa Rosa, Santa Rosa horkelia, Sonoma horkelia, thin-lobed, thin-lobed horkelia
Point Reyes horkelia
ascending to erect, 1–4 dm, hairs ± spreading.
± decumbent to ascending, 1–3.5(–4.5) dm, hairs spreading to ascending.
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 to nearly cylindric, 4–12(–15) × 1–2.5(–3) cm;
stipules entire or basally lobed;
leaflets 5–10(–12) per side, ± overlapping especially distally, cuneate, 7–12 × 5–10 mm, nearly as wide as long, divided 1/3–1/2 to midrib into (3–)5–10 acute to obtuse teeth, villous.
2–5.
3–5.
open to congested, flowers arranged individually and in glomerules, these sometimes subcapitate.
usually congested, flowers usually arranged in dense corymbiform clusters.
1–6 mm.
1–6 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.
10–15 mm diam.;
epicalyx bractlets lanceolate, 2.5–4.5 × 1 mm, ± 2/3 length of sepals, entire;
hypanthium 1.2–1.5 × 4–5 mm, less than 1/2 as deep as wide, interior pilose;
sepals ± reflexed, lanceolate, 3–6 mm;
petals narrowly oblanceolate to narrowly oblong, 4–7 × 2 mm, apex obtuse to rounded, rarely truncate;
filaments 1–2.8 × 0.2–0.6 mm, anthers 0.6–0.9 mm;
carpels 20–30;
styles 2–4 mm.
light brown, 1.5 mm, smooth or slightly rugose.
brown, 1.5–2 mm, smooth to slightly rugose.
= 28.
= 56.
Horkelia tenuiloba
Horkelia marinensis
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 marinensis occurs in three population clusters along the coast of California: near Fort Bragg and Rockport in Mendocino County, on Point Reyes Peninsula in Marin County, and from Santa Cruz and (historically) San Mateo counties. The last population cluster has often been confused with H. cuneata var. sericea; plants of it have more deeply and apically toothed, cuneate leaflets and longer, silkier hairs. It is also the basis for the attribution by J. H. Thomas (1961) of H. rydbergii (as H. bolanderi subsp. parryi) to the Santa Cruz Mountains. The three population clusters differ somewhat in vestiture, evident glandularity, and leaflet shape and size; further studies may indicate that varietal status is justified. References to H. marinensis in Sonoma County (M. G. Barbour 1970) are based on specimens of Acaena pinnatifida var. californica; reports from southern Mendocino County (G. L. Smith and C. R. Wheeler 1990–1991) are based on misidentifications of H. californica and H. tenuiloba.
Horkelia marinensis is by far the most aromatic member of the genus; the odor, which has been compared to that of a beehive, often can be perceived even before the plants are located, especially on sunny days. Plants do relatively well in cultivation, forming spreading mats with flowers that are strongly attractive to both native bees and honeybees.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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