Arabis georgiana |
Arabis mcdonaldiana |
|
---|---|---|
Georgia rockcress |
Mcdonald's rock-cress |
|
Habit | 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. | 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 (rosette), erect, unbranched or branched (few) distally, 3–7 dm, (hirsute basally, glabrous distally). |
simple or few from base (caudex), erect, unbranched, (0.6–)1.5–3(–4) dm, (glabrous). |
Basal leaves | 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 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 | 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 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 | often simple. |
simple, (dense). |
Flowers | 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, 4–8 × 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 | erect to erect-ascending, 7–16 mm, (glabrous). |
ascending to suberect, 3–10(–13) mm. |
Fruits | 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. |
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 throughout, oblong, 0.9–1.9 × 0.5–0.7 mm; wing to 0.1 mm wide distally. |
narrowly winged distally or, rarely, not winged, oblong, 1.5–2.2 × 1–1.3 mm, wing 0.1–0.2 mm wide. |
Arabis georgiana |
Arabis mcdonaldiana |
|
Phenology | Flowering Mar–Apr. | Flowering May–Jun. |
Habitat | Stream banks, roadsides | Serpentine scrap and slopes, red serpentinized soil |
Elevation | 0-200 m (0-700 ft) | 200-1800 m (700-5900 ft) |
Distribution |
AL; GA |
CA; OR
|
Discussion | 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.) |
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. 261. | FNA vol. 7, p. 265. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | A. blepharophylla var. mcdonaldiana, A. serpentinicola | |
Name authority | R. M. Harper: Torreya 3: 88. (1903) | Eastwood: Bull. Torrey Bot. Club 30: 488, unnumb. fig. (p. 489). (1903) |
Web links |
|