ROSACEAE

ROSE FAMILY

Annual to tree
Leaves simple to pinnately to palmately compound, generally alternate; stipules free to fused, persistent to deciduous
Inflorescence: cyme, raceme, panicle, or flowers solitary
Flower generally bisexual, radial; hypanthium free or fused to ovary, saucer- to funnel-shaped, often with bractlets alternate with sepals; sepals generally 5; petals generally 5, free; stamens (0)5–many, pistils (0)1–many, simple or compound; ovary superior to inferior, styles 1–5
Fruit: achene, follicle, drupe, pome, or blackberry- to raspberry-like
Seeds generally 1–5
Genera in family: 110 genera, ± 3000 species: worldwide, especially temp. Many cultivated for ornamental and fruit, especially Cotoneaster , Fragaria , Malus , Prunus , Pyracantha, Rosa , and Rubus
Reference: [Robertson 1974 J Arnold Arbor 55:303–332,344–401,611–662]
Family description, key to genera by Barbara Ertter and Dieter H. Wilken.

HORKELIA

Barbara Ertter

Perennial, generally ± glandular, generally resinous-smelling; caudex generally branched
Stem generally ascending to erect
Leaves generally basal, odd-1-pinnate, generally ± flat; cauline alternate, reduced upward; uppermost lateral leaflets generally ± fused with terminal
Inflorescence: cyme, open or of dense clusters; pedicels generally straight
Flower: hypanthium a ± flat-bottomed cup, width ± 2 X length; bractlets 5, generally 2/3 sepals; sepals 5, often reflexed; petals 5, generally ± = sepals, blunt, white; stamens 10, filaments flat, often forming a tube; pistils 2–many, ovaries superior, styles jointed below fruit tip, ± thicker at base
Fruit: achene
Species in genus: 19 species: w North America
Etymology: (J. Horkel, German plant physiologist, 1769–1846)
Data apply to basal leaves, pressed hypanthia.

Native

H. tenuiloba (Torr.) A. Gray

THIN-LOBED HORKELIA

Plant loosely matted, generally ± green
Stem < 40 cm; hairs ± spreading
Leaf 5–15 cm, often ± cylindric; leaflets generally 8–15 per side, ± crowded, 3–10 mm, divided > 1/2 to base into 3–8 linear to oblanceolate lobes, hairs sparse to dense
Inflorescence dense or ± open, few–many-flowered; pedicels generally 1–6 mm
Flower: hypanthium width 3–4.5 mm, > 2 X length, inner wall ± hairy; bractlets 0.5–1 mm wide, linear-lanceolate; sepals 3–5 mm; petals ± 4 mm, oblanceolate; filaments ± 1.5–2 mm, bases ± 0.5 mm wide, anthers ± 0.5 mm; pistils 10–25, styles ± 2 mm
Fruit ± 1.5 mm
Chromosomes: 2n=28
Ecology: UNCOMMON. ± sandy soils, open chaparral
Elevation: 50–500 m.
Bioregional distribution: c&s North Coast, c&s Outer North Coast Ranges, nw San Francisco Bay Area
Horticultural information: DRN, IRR: 5, 7, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24; GRCVR.