Arabis georgiana
Arabis modesta
Georgia rockcress
modest rock-cress, Rogue Canyon rock-cress
simple or few from base (rosette), erect, unbranched or branched (few) distally, 3–7 dm, (hirsute basally, glabrous distally).
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).
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.
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.
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.
(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.
often simple.
simple, (dense).
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.
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.
erect to erect-ascending, 7–16 mm, (glabrous).
ascending to divaricate, 7–18(–25) mm.
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.
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.
narrowly winged throughout, oblong, 0.9–1.9 × 0.5–0.7 mm;
wing to 0.1 mm wide distally.
winged distally, oblong, 1.7–2.2 × 0.9–1.2 mm;
wing 0.2–0.5 mm wide.
= 32.
Arabis georgiana
Arabis modesta
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.)
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.)
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USDA Plants Database
CA
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