Flora of North America species comparison

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Arabis mcdonaldiana

Mcdonald's rock-cress
Habit Perennials; (caudex simple or branched, covered with persistent petiolar remains); usually glabrous, rarely sparsely pubescent, trichomes simple, (to 0.5 mm), not bulbous-based.
Stems

simple or few from base (caudex), erect, unbranched, (0.6–)1.5–3(–4) dm, (glabrous).
Basal leaves

petiole 0.3–1.5 cm;

blade oblanceolate to obovate, (0.5–)1–3(–4) cm × (2–)3–6(–10) mm, margins entire, repand, or obtusely dentate, apex obtuse, surfaces sometimes with individual trichomes terminating some or all leaf teeth.
Cauline leaves

(2 or) 3–5 (or 6);

blade oblong, 0.3–1(–1.2) cm × 1–3 mm, base not auriculate, margins entire or repand, apex obtuse, surfaces glabrous.
Racemes

simple, (dense).
Flowers

sepals (purple), oblong, 4–8 × 1.5–2.5 mm, lateral pair saccate basally;

petals purple, spatulate, 8–16 × 2–5 mm, apex obtuse;

filaments 4–8 mm;

anthers oblong, 1.5–2 mm.
Fruiting pedicels

ascending to suberect, 3–10(–13) mm.
Fruits

ascending to suberect, not torulose, sometimes slightly curved, 2–4 cm × 1.5–2 mm;

valves each with prominent midvein extending full length;

ovules 20–34 per ovary;

style 0.3–1.5 mm.
Seeds

narrowly winged distally or, rarely, not winged, oblong, 1.5–2.2 × 1–1.3 mm, wing 0.1–0.2 mm wide.

Arabis mcdonaldiana
Phenology Flowering May–Jun.
Habitat Serpentine scrap and slopes, red serpentinized soil
Elevation 200-1800 m (700-5900 ft)
Distribution
from FNA
CA; OR
[WildflowerSearch map]
Discussion

Of conservation concern.

Arabis mcdonaldiana is known in California from Del Norte, Mendocino, and Siskiyou counties, and in Oregon from Curry and Jackson counties. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 265.
Parent taxa Brassicaceae > tribe Arabideae > Arabis
Sibling taxa
A. aculeolata, A. alpina, A. blepharophylla, A. caucasica, A. crucisetosa, A. eschscholtziana, A. furcata, A. georgiana, A. modesta, A. nuttallii, A. olympica, A. oregana, A. patens, A. pycnocarpa
Synonyms A. blepharophylla var. mcdonaldiana, A. serpentinicola
Name authority Eastwood: Bull. Torrey Bot. Club 30: 488, unnumb. fig. (p. 489). (1903)
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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