Arabis modesta
modest rock-cress, Rogue Canyon rock-cress
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 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.
(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.
simple, (dense).
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.
ascending to divaricate, 7–18(–25) 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.
winged distally, oblong, 1.7–2.2 × 0.9–1.2 mm;
wing 0.2–0.5 mm wide.
= 32.
Arabis modesta
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.)
CA
OR
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
