Arabis pycnocarpa |
Arabis furcata |
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blushing rock-cress, cream-flower rock-cress, hairy eared-rockcress, hairy rockcress, slender rock cress |
Cascade rock-cress, Columbia Gorge rockcress, fork-hair rock-cress |
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Habit | Biennials or perennials; (caudex branched); usually densely hirsute (at least basally), rarely glabrescent, trichomes simple mixed with stalked or sessile, forked ones. | Perennials; (caudex simple or branched, covered with persistent petiolar remains); glabrous or sparsely pubescent, trichomes simple or short-stalked, forked (0.3–1 mm), these rarely mixed with fewer, unequal 3-rayed ones. | ||||
Stems | simple or several from base (rosette), erect, often branched distally, 1–8 dm, (pilose with trichomes appressed, malpighiaceous, or minutely stalked, forked, or hirsute basally with trichomes simple and minutely stalked, forked, sometimes almost exclusively pubescent with forked submalpighiaceous trichomes). |
simple or few from base (caudex), erect, usually unbranched, rarely branched (few) distally, (0.7–)1–3.8(–4.5) dm, (glabrous throughout or sparsely pubescent basally to distally). |
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Basal leaves | petiole 0.5–2 cm, (ciliate or not); blade spatulate, oblanceolate, or oblong, (0.8–)1.5–8 cm × (5–)10–25 mm, margins entire, repand, or dentate, apex obtuse or acute, surfaces sparsely to densely pubescent, trichomes sessile or stalked, simple or forked, and/or stellate. |
petiole (0.4–)1–3(–4.5) cm, (glabrous or sparsely ciliate); blades oblanceolate, spatulate, or obovate, (0.7–)1.2–3 cm × 5–17(–22) mm, margins entire or dentate, (often ciliate), apex obtuse, surfaces glabrous or sparsely pubescent, trichomes short-stalked, forked and simple. |
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Cauline leaves | (7–)10–45(–61), (overlapping or not); blade ovate to oblong or lanceolate, rarely linear, (1–)1.5–6(–8) cm × (1–)3–20(–25) mm, base subcordate or auriculate (auricles obtuse or subacute), margins dentate or entire, apex acute or obtuse, surfaces hirsute or adaxially glabrescent. |
(2 or) 3–5 (or 6); blade linear, oblong, obovate, or oblanceolate, 0.7–3(–4) cm × 3–8 mm, base cuneate, not auriculate, margins usually entire, rarely few-toothed, apex obtuse, surfaces usually glabrous, rarely margins ciliate. |
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Racemes | often simple. |
simple, (dense or lax). |
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Flowers | sepals oblong, 2.5–4 × 0.5–1.5 mm, lateral pair not saccate basally; petals white, linear-oblanceolate or narrowly spatulate, 3.5–5(–5.5) × 1–2(–2.5) mm, apex obtuse; filaments 2.5–4 mm; anthers oblong, 0.7–1 mm. |
sepals (greenish), oblong, 3–4 × 1.5–2 mm, (usually glabrous, rarely with few trichomes subapically), lateral pair saccate basally; petals white, spatulate, 7–11 × 2.5–4 mm, apex rounded; filaments 3.5–5 mm; anthers oblong, 0.8–1 mm. |
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Fruiting pedicels | erect to erect-ascending, (2–)3–8(–12) mm (glabrous or sparsely pubescent). |
suberect, ascending, or divaricate, (2–)4–17(–22) mm, (glabrous). |
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Fruits | erect to erect-ascending, (often appressed to rachis), torulose, (3.5–)4–6(–6.5) cm × 0.8–1(–1.2) mm; valves each with obscure or somewhat prominent midvein extending to the middle; ovules (54–)60–86 per ovary; style (0.2–)0.5–1(–1.3) mm, (slender). |
ascending to suberect, (not appressed to rachis), slightly torulose, sometimes slightly curved, strongly flattened, (2–)2.5–4(–4.6) cm × 1.7–2.2 mm; valves each with prominent midvein extending full length; ovules 14–26 per ovary; style 0.5–1.2(–1.6) mm, (slender). |
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Seeds | narrowly winged throughout, oblong or suborbicular, (0.8–)1–1.5(–1.7) × 0.8–1.3 mm; wing to 0.2 mm wide distally. |
winged distally, oblong to broadly ovate, (1.5–)1.8–2.5(–3) × 1–1.3 mm; wing (0.2–)0.4–0.8(–1) mm wide. |
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Arabis pycnocarpa |
Arabis furcata |
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Phenology | Flowering May–Jul(-Aug). | |||||
Habitat | Open slopes, alpine meadows, cliffs, ridge crests | |||||
Elevation | (50-)1000-2100 m ((200-)3300-6900 ft) | |||||
Distribution |
AK; AZ; CA; CO; CT; IA; ID; IL; IN; KS; MA; ME; MI; MN; MO; MT; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; SD; TN; UT; VA; VT; WI; WV; WY; AB; BC; MB; NB; NL; NS; NT; ON; QC; SK; YT; Asia
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OR; WA
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Discussion | Varieties 2 (2 in the flora). M. Hopkins (1937) synthesized earlier works on Arabis pycnocarpa and concluded that it is different from the European A. hirsuta. Both R. C. Rollins (1941, 1993) and G. A. Mulligan (1996) considered the North American and European plants different varieties of A. hirsuta; Mulligan recognized var. hirsuta in North America and Rollins did not. After examining thousands of specimens from Europe, Asia, and North America, I conclude that Hopkins was correct in treating the North American plants as a different species, A. pycnocarpa. The European A. hirsuta is a diploid (2n = 16) that has fruits 1.5–4 cm, stout styles 0.1–0.5 mm, prominent midvein extending the full length of the fruit valve, and 30–40(–44) ovules/seeds per ovary/fruit. By contrast, A. pycnocarpa is a tetraploid (2n = 32) that has fruits (3.5–)4–6(–6.5) cm, often slender styles (0.2–)0.5–1(–1.3) mm, obscure midvein hardly extending to the middle of the fruit valve, and ovules/seeds (54–)60–86 per ovary/fruit. Hopkins listed other differences in the number of cauline leaves and the development of seed wing, but these do not hold. Mulligan treated the perennial North American plants with minute styles as var. hirsuta and the biennial ones with longer styles as var. pycnocarpa. Habit and style length are not correlated at all, and one finds both biennials and perennials flowering in the same population. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Arabis furcata is known in Washington from Chelan, Kittitas, Klickitat, Okanogan, Skamania, and Yakima counties, and in Oregon from Clackamas, Hood River, Multnomah, and Wasco counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 259. | FNA vol. 7, p. 262. | ||||
Parent taxa | ||||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | A. hirsuta subsp. pycnocarpa, A. hirsuta var. pycnocarpa | A. suksdorfii | ||||
Name authority | M. Hopkins: Rhodora 39: 112, plate 458, figs. 1–3. (1937) | S. Watson: Proc. Amer. Acad. Arts 17: 362. (1882) | ||||
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