Flora of North America species comparison

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Arabis olympica

Arabis oregana

Olympics rockcress

Oregon rock-cress
Habit Perennials; (caudex branched, covered with persistent petiolar remains); moderately pubescent, trichomes simple or short-stalked, forked, (to 0.6 mm). Perennials; (caudex simple or branched, with some persistent petiolar remains); sparsely to moderately pubescent, trichomes bulbous-based, simple and long-stalked, forked, (to 2 mm), these often mixed with fewer 3-rayed, stalked stellate ones.
Stems

simple or few from base (caudex), erect, unbranched, 0.7–1.1 dm, (pubescent throughout, trichomes short-stalked, forked).

simple or few from base (caudex), erect, unbranched distally, (0.6–)1.7–4.5(–5) dm, (usually pubescent throughout, rarely subglabrate, coarsely hirsute, trichomes simple, mixed with forked ones).
Basal leaves

petiole 0.3–0.6 cm, (sparsely ciliate);

blades oblanceolate to obovate, 0.4–1cm × 2–7 mm, margins entire or repand, (ciliate), apex obtuse, surfaces sparsely pubescent, trichomes simple and forked.

petiole 0.5–2(–3) cm, (ciliate);

blade oblanceolate to obovate, (1–)2–5(–9) cm × (5–)8–18(–22) mm, margins entire or repand to dentate, (ciliate), apex obtuse, surfaces pubescent or glabrous, trichomes simple and forked, sometimes mixed with 3-rayed stellate ones.
Cauline leaves

4–6;

blade oblong, 0.6–0.8 cm × 2–3 mm, base not auriculate, margins entire, (ciliate), apex obtuse.

3–6 (or 7);

blade oblong, 1–3(–6) cm × 2–7(–15) mm, base not auriculate, margins entire or dentate, (ciliate or not), apex obtuse, surfaces pubescent as basal leaves or glabrous.
Racemes

simple, (dense).

simple, (dense).
Flowers

sepals (greenish), ovate, 1.5 × 0.5 mm, lateral pair not saccate basally, (glabrous);

petals white, oblanceolate, 3.5–4 × 1 mm, apex rounded.

sepals (purple), oblong, (5–)6–8 × 1.5–2 mm, lateral pair saccate basally;

petals purple or pink, spatulate, (10–)12–15(–16) × (3–)4–5 mm, apex obtuse;

filaments (4–)5–8 mm;

anthers narrowly oblong, 1.2–1.8 mm.
Fruiting pedicels

erect, (subappressed to rachis), 5–6.5 mm, (glabrous).

ascending to erect, 5–10 mm, (pubescent or glabrous).
Fruits

erect, (appressed to rachis), slightly torulose, 2–2.3 cm × 1 mm;

valves each with distinct midvein extending full length;

ovules 28–34 per ovary;

style 0.2–0.3 mm, (stout).

erect or nearly so, slightly torulose, (3–)4.5–6 cm × 1.5–2 mm;

valves each with prominent midvein;

ovules 24–30 per ovary;

style 0.5–1 mm.
Seeds

winged distally, oblong, ca. 1 × 0.5 mm;

wing ca. 0.1 mm wide.

narrowly winged distally or not winged, oblong, 1.8–2.2 × ca. 1 mm;

wing ca. 0.1 mm wide.
2n

= 32.

Arabis olympica

Arabis oregana
Phenology Flowering Aug. Flowering Apr–May.
Habitat Talus slopes near glacier Moist granitic soil, rocky hillsides, chaparrals, steep banks
Elevation ca. 1400 m (ca. 4600 ft) 500-1000(-1400) m (1600-3300(-4600) ft)
Distribution
from FNA
WA
[BONAP county map]
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
Discussion

Arabis olympica, which is known from two collections, J. B. Flett s.n. (holotype, US; isotype, WS) and N. Buckingham 1577 (WS) that were made from Jefferson and Clallam counties, respectively, was reduced by R. C. Rollins (1936, 1941, 1993) to a variety of A. furcata. An examination of the type collections of both species reveals that they are distinct. Although the fruits and seeds of A. olympica are not fully mature, they are clearly different in width and orientation from those of A. furcata at the same developmental stage. The striking differences in fruit width and orientation, stem indument, and seed and flower size support their maintenance as distinct species. Although both species grow in Washington, the range of A. olympica seems to be restricted to Clallam and Jefferson counties and is disjunct from Chelan, Kittitas, and Yakima counties, where A. furcata grows.

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

Arabis oregana is known from Napa and Siskiyou counties (California) and Jackson County (Oregon).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 263. FNA vol. 7, p. 264.
Parent taxa Brassicaceae > tribe Arabideae > Arabis Brassicaceae > tribe Arabideae > Arabis
Sibling taxa
A. aculeolata, A. alpina, A. blepharophylla, A. caucasica, A. crucisetosa, A. eschscholtziana, A. furcata, A. georgiana, A. mcdonaldiana, A. modesta, A. nuttallii, A. oregana, A. patens, A. pycnocarpa
A. aculeolata, A. alpina, A. blepharophylla, A. caucasica, A. crucisetosa, A. eschscholtziana, A. furcata, A. georgiana, A. mcdonaldiana, A. modesta, A. nuttallii, A. olympica, A. patens, A. pycnocarpa
Synonyms A. furcata var. olympica A. purpurascens, A. furcata var. purpurascens
Name authority Piper: Contr. U.S. Natl. Herb. 16: 208. (1913) Rollins: Rhodora 43: 349. (1941)
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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