Arabis modesta |
Arabis eschscholtziana |
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modest rock-cress, Rogue Canyon rock-cress |
Eschscholtz's hairy rock-cress, Eschscholtz's rockcress, hairy rockcress, Pacific coast rockcress |
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Habit | Perennials; (caudex usually simple, rarely branched, covered with persistent petiolar remains); sparsely to densely pubescent, trichomes short-stalked, cruci-form, or 3-rayed stellate, (0.3–0.5 mm). | Biennials or perennials; (caudex branched); usually densely hirsute (at least basally), trichomes simple or stalked, forked, sometimes glabrescent with mostly simple ones. |
Stems | simple or few from base (caudex), erect, usually unbranched, rarely branched (few) distally, 2.2–5.5(–6.7) dm, (usually pubescent throughout, rarely subglabrate distally, trichomes stellate). |
simple or several from base (rosette), erect, often branched distally, 2–7(–10) dm, (hirsute basally, trichomes simple and minutely stalked, forked, rarely almost exclusively glabrous). |
Basal leaves | petiole 1–4(–5) cm, (rarely minutely ciliate near base); blade oblanceolate to obovate, (0.8–)2–4.5(–6) cm × (4–)10–20(–25) mm, margins entire, repand, or dentate, (not ciliate), apex obtuse, surfaces pubescent, trichomes short-stalked, stellate. |
petiole 0.7–3 cm, (ciliate or not); blade broadly spatulate to narrowly oblanceolate, 1.2–10 cm × 7–30 mm, margins entire or dentate, apex obtuse or acute, surfaces usually pubescent, sometimes glabrous, trichomes simple, forked and stalked, stellate. |
Cauline leaves | (2–)4–6(–9); blade oblong or ovate, 1–3.5(–4.5) cm × (3–)6–10(–20) mm, base not auriculate, margins entire, repand, or dentate, apex obtuse or acute, surfaces pubescent, trichomes short-stalked, stellate. |
(2–)4–12(–18), (well-spaced or, rarely, overlapping); blade ovate to oblong or lanceolate, 1.5–6.5(–10) cm × 5–30 mm, base auriculate, margins dentate or entire, apex acute or obtuse, surfaces sparsely hirsute or glabrous. |
Racemes | simple, (dense). |
simple or branched. |
Flowers | sepals (purple), oblong, (4–)5–6.5(–8) × 1.5–2 mm, lateral pair saccate basally; petals purple, spatulate, (10–)12–16(–20) × 4–6(–7) mm, apex rounded; filaments (4–)5–8 mm; anthers narrowly oblong, 1.3–2 mm. |
sepals oblong, 3.5–5 × 1.2–2 mm, lateral pair saccate basally; petals white, rarely pink, linear-oblanceolate or narrowly spatulate, (5.5–) 6.5–9(–10) × 1.5–3 mm, apex obtuse; filaments 3.5–6 mm; anthers oblong, 0.7–1 mm. |
Fruiting pedicels | ascending to divaricate, 7–18(–25) mm. |
erect to erect-ascending, 3.5–10(–15) mm, (glabrous or sparsely pubescent). |
Fruits | suberect to divaricate, sometimes slightly curved, slightly torulose, (2.8–)3.5–6 cm × 1.5–2 mm; valves each with prominent midvein extending to middle or full length; ovules 20–34 per ovary; style 0.5–1(–1.5) mm. |
erect to erect-ascending, (often appressed to rachis), torulose, 3.5–6.5 cm × 1.2–1.8(–2) mm; valves each with prominent midvein extending full length or to middle; ovules 54–80 per ovary; style (0.1–)0.3–1 mm. |
Seeds | winged distally, oblong, 1.7–2.2 × 0.9–1.2 mm; wing 0.2–0.5 mm wide. |
usually narrowly winged throughout or only distally, rarely not winged, oblong or suborbicular, 1–1.8 × 0.9–1.3 mm; wing to 0.2 mm wide distally. |
2n | = 32. |
= 32, 64. |
Arabis modesta |
Arabis eschscholtziana |
|
Phenology | Flowering Mar–Apr(-May). | Flowering (Apr-)May–Jul. |
Habitat | Moist shaded banks, slopes, rocky canyon walls, talus, basaltic bluffs | Rocky slopes, crevices, and ledges, meadows, moist banks and grounds, granitic soil, wooded slopes |
Elevation | 150-500 m (500-1600 ft) | 0-2800 m (0-9200 ft) |
Distribution |
CA; OR
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AK; CA; ID; MT; NV; OR; UT; WA; WY; AB; BC; YT
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Discussion | Arabis modesta, known only from Napa, Siskiyou, and Yolo counties (California), and Jackson and Josephine counties (Oregon), and the following four species form a well-defined group easily separated from the first nine species above by their large, purple petals. Arabis modesta is readily distinguished from other purple-flowered Arabis by having very fine, short-stalked cruciform and 3-rayed, instead of simple and 2-rayed, forked trichomes. Arabis blepharophylla has broadly winged, orbicular seeds, and the other purple-flowered species (A. aculeolata, A. mcdonaldiana, A. oregana) have oblong seeds that are not winged or narrowly winged distally. The lines separating these three species are not as well-defined as those of A. blepharophylla and A. modesta, and further studies are needed to resolve them. I prefer to maintain all five species of purple-flowered Arabis as distinct until thorough molecular and hybridization studies are conducted. In the absence of such studies, it is unwise to make any nomenclatural changes. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
G. A. Mulligan (1996) recognized Arabis eschscholtziana as a distinct species; R. C. Rollins (1941, 1993) treated it as a variety of A. hirsuta. As discussed under A. pycnocarpa, A. hirsuta does not occur in North America, and the characters separating all three species (see key to species), as well as the different ploidy levels, support Mulligan’s conclusion. Both M. Hopkins (1937) and R. C. Rollins (1941, 1993) recognized the glabrous or subglabrate forms native to North America as a distinct variety, var. glabrata; G. A. Mulligan (1996) did not accord such forms any taxonomic status. Glabrous and subglabrate forms occur in both Arabis eschscholtziana and A. pycnocarpa and sometimes even within a population that has moderately to densely pubescent forms. I support Mulligan’s view in not recognizing the glabrous forms as an infraspecific taxon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 264. | FNA vol. 7, p. 261. |
Parent taxa | Brassicaceae > tribe Arabideae > Arabis | Brassicaceae > tribe Arabideae > Arabis |
Sibling taxa | ||
Synonyms | A. hirsuta subsp. eschscholtziana, A. hirsuta var. eschscholtziana, A. hirsuta var. glabrata, A. ovata var. glabrata, A. pycnocarpa var. glabrata, A. rupestris, A. stelleri var. eschscholtziana, Turritis spathulata | |
Name authority | Rollins: Rhodora 43: 350. (1941) | Andrzejowski: in C. F. von Ledebour, Fl. Altaica 3: 25. (1831) |
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