Flora of North America species comparison

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Horkelia tridentata var. tridentata

Rosaceae subfam. rosoideae
Photo is of parent taxon

cluster horkelia, three tooth horkelia
Habit Herbs, shrubs, or subshrubs.
Stems

decumbent to nearly erect, 1–4(–7) dm.

Leaves

alternate, rarely opposite, pinnately compound, sometimes simple or palmately compound;

stipules present, rarely absent.
Inflorescences

composed of 1+ 5–40-flowered ± capitate glomerules, these sometimes expanding with age.

Flowers

4–9 mm diam.;

hypanthium 2–3.5(–5) mm diam., interior glabrous;

petals linear to oblanceolate, (1.5–)2–3.5(–4.5) × 0.3–1 mm, usually ± equal to or longer than sepals, apex acute to obtuse;

filaments 0.5–1(–2) × 0.1–0.2 mm, anthers 0.2–0.3(–0.4) mm;

styles 1–2 mm.

torus usually enlarged, sometimes small or absent;

carpels 1–260(–450), distinct, free, styles distinct, rarely connate (Roseae);

ovules 1(or 2), collateral (Rubeae) or superposed (Fallugia, Filipendula).
Fruits

achenes or aggregated achenes sometimes with fleshy, urn-shaped hypanthium or enlarged torus, sometimes aggregated drupelets;

styles persistent or deciduous, not elongate (elongate but not plumose in Geum).
Achenes

1.5–2 mm, lightly rugose.

x

= 7(8).
2n

= 28.

Horkelia tridentata var. tridentata

Rosaceae subfam. rosoideae
Phenology Flowering spring–summer.
Habitat Open areas, primarily in sagebrush communities and conifer woodlands, mainly on granitic or volcanic soil
Elevation 300–2500 m (1000–8200 ft)
Distribution
from FNA
CA; OR
[BONAP county map]
North America; Mexico; Central America; South America; West Indies; Bermuda; Eurasia; Africa; Atlantic Islands; Indian Ocean Islands; Pacific Islands; Australia
Discussion

Variety tridentata occurs throughout the Cascade Mountains and Sierra Nevada of California, and barely extends into southern Oregon near Ashland, Josephine County, where the presence of distal cauline glands on some plants indicates possible introgression with Horkelia congesta. A specimen from Glendale, Oregon, (Jones s.n., POM) that was annotated and cited by D. D. Keck (1938) as H. congesta subsp. nemorosa is fully comparable to the Ashland material of var. tridentata; the apparent disjunction in Douglas County needs to be confirmed.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Variation in the number of genera in subfam. Rosoideae is due to differences in generic delimitation between D. Potter et al. (2007) and the authors of some Potentilleae genera. Cyanogenic glycosides and sorbitol are absent in the subfamily.

Tribes 6, genera 28–35, species ca. 1600 (6 tribes, 26 genera, 302 species, including 1 hybrid, in the flora)

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 9, p. 269. FNA vol. 9, p. 23. Author: Luc Brouillet.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae > Horkelia tridentata Rosaceae
Sibling taxa
H. tridentata var. flavescens
Subordinate taxa
Synonyms Potentilla tilingii
Name authority unknown Arnott: Botany, 107. (1832)
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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