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Cascade rock-cress, Columbia Gorge rockcress, fork-hair rock-cress

Georgia rockcress

Habit 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. Biennials; sparsely to moderately hirsute (at least basally), trichomes simple, mixed with fewer, short-stalked, forked ones, subsessile cruciform or 3-rayed stellate trichomes commonly on abaxial blade surfaces, sometimes plants glabrous distally.
Stems

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).

simple or few from base (rosette), erect, unbranched or branched (few) distally, 3–7 dm, (hirsute basally, glabrous distally).

Basal leaves

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.

petiole 0.5–2 cm, (ciliate or not);

blade spatulate, oblanceolate, or obovate, 1.5–6 cm × 5–15 mm, margins dentate, apex obtuse or acute, abaxial surface moderately to sparsely pubescent, trichomes subsessile stellate, adaxial surface subglabrate or sparsely stellate.

Cauline leaves

(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.

7–26;

blade oblong, lanceolate, or linear-lanceolate, 1.5–7 cm × 3–18 mm, base auriculate to subamplexicaul, margins dentate or entire, apex acute or obtuse, pubescent as basal leaves except distalmost leaves often glabrous.

Racemes

simple, (dense or lax).

often simple.

Flowers

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.

sepals oblong, 2.5–4.5 × 1–1.5 mm, lateral pair subsaccate basally;

petals white, narrowly spatulate or oblanceolate, 6–9 × 1–1.5 mm, apex obtuse;

filaments 3–4.5 mm;

anthers oblong, 0.8–1 mm.

Fruiting pedicels

suberect, ascending, or divaricate, (2–)4–17(–22) mm, (glabrous).

erect to erect-ascending, 7–16 mm, (glabrous).

Fruits

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).

erect to erect-ascending, (often subappressed to rachis), smooth, 4–7 cm × 0.7–0.8 mm;

valves each with midvein extending full length or to middle;

ovules 38–44 per ovary;

style 0.7–1.8 mm.

Seeds

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.

narrowly winged throughout, oblong, 0.9–1.9 × 0.5–0.7 mm;

wing to 0.1 mm wide distally.

Arabis furcata

Arabis georgiana

Phenology Flowering May–Jul(-Aug). Flowering Mar–Apr.
Habitat Open slopes, alpine meadows, cliffs, ridge crests Stream banks, roadsides
Elevation (50-)1000-2100 m ((200-)3300-6900 ft) 0-200 m (0-700 ft)
Distribution
from FNA
OR; WA
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; GA
[BONAP county map]
Discussion

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.)

Of conservation concern.

Arabis georgiana is most closely related to A. pycnocarpa, from which it is easily distinguished by having narrower fruits, longer petals, and subsessile cruciform or 3-rayed trichomes on abaxial surfaces of basal leaves. It is known only in Alabama from Bibb and Elmore counties and in Georgia from Stewart County.

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

Source FNA vol. 7, p. 262. FNA vol. 7, p. 261.
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. georgiana, A. mcdonaldiana, A. modesta, A. nuttallii, A. olympica, A. oregana, A. patens, A. pycnocarpa
A. aculeolata, A. alpina, A. blepharophylla, A. caucasica, A. crucisetosa, A. eschscholtziana, A. furcata, A. mcdonaldiana, A. modesta, A. nuttallii, A. olympica, A. oregana, A. patens, A. pycnocarpa
Synonyms A. suksdorfii
Name authority S. Watson: Proc. Amer. Acad. Arts 17: 362. (1882) R. M. Harper: Torreya 3: 88. (1903)
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