Arabis georgiana |
Arabis eschscholtziana |
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Georgia rockcress |
Eschscholtz's hairy rock-cress, Eschscholtz's rockcress, hairy rockcress, Pacific coast rockcress |
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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. | Biennials or perennials; (caudex branched); usually densely hirsute (at least basally), trichomes simple or stalked, forked, sometimes glabrescent with mostly simple ones. |
Stems | simple or few from base (rosette), erect, unbranched or branched (few) distally, 3–7 dm, (hirsute basally, glabrous distally). |
simple or several from base (rosette), erect, often branched distally, 2–7(–10) dm, (hirsute basally, trichomes simple and minutely stalked, forked, rarely almost exclusively 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 0.7–3 cm, (ciliate or not); blade broadly spatulate to narrowly oblanceolate, 1.2–10 cm × 7–30 mm, margins entire or dentate, apex obtuse or acute, surfaces usually pubescent, sometimes glabrous, trichomes simple, forked and stalked, stellate. |
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–)4–12(–18), (well-spaced or, rarely, overlapping); blade ovate to oblong or lanceolate, 1.5–6.5(–10) cm × 5–30 mm, base auriculate, margins dentate or entire, apex acute or obtuse, surfaces sparsely hirsute or glabrous. |
Racemes | often simple. |
simple or branched. |
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 oblong, 3.5–5 × 1.2–2 mm, lateral pair saccate basally; petals white, rarely pink, linear-oblanceolate or narrowly spatulate, (5.5–) 6.5–9(–10) × 1.5–3 mm, apex obtuse; filaments 3.5–6 mm; anthers oblong, 0.7–1 mm. |
Fruiting pedicels | erect to erect-ascending, 7–16 mm, (glabrous). |
erect to erect-ascending, 3.5–10(–15) mm, (glabrous or sparsely pubescent). |
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. |
erect to erect-ascending, (often appressed to rachis), torulose, 3.5–6.5 cm × 1.2–1.8(–2) mm; valves each with prominent midvein extending full length or to middle; ovules 54–80 per ovary; style (0.1–)0.3–1 mm. |
Seeds | narrowly winged throughout, oblong, 0.9–1.9 × 0.5–0.7 mm; wing to 0.1 mm wide distally. |
usually narrowly winged throughout or only distally, rarely not winged, oblong or suborbicular, 1–1.8 × 0.9–1.3 mm; wing to 0.2 mm wide distally. |
2n | = 32, 64. |
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Arabis georgiana |
Arabis eschscholtziana |
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Phenology | Flowering Mar–Apr. | Flowering (Apr-)May–Jul. |
Habitat | Stream banks, roadsides | Rocky slopes, crevices, and ledges, meadows, moist banks and grounds, granitic soil, wooded slopes |
Elevation | 0-200 m (0-700 ft) | 0-2800 m (0-9200 ft) |
Distribution |
AL; GA |
AK; CA; ID; MT; NV; OR; UT; WA; WY; AB; BC; YT
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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.) |
G. A. Mulligan (1996) recognized Arabis eschscholtziana as a distinct species; R. C. Rollins (1941, 1993) treated it as a variety of A. hirsuta. As discussed under A. pycnocarpa, A. hirsuta does not occur in North America, and the characters separating all three species (see key to species), as well as the different ploidy levels, support Mulligan’s conclusion. Both M. Hopkins (1937) and R. C. Rollins (1941, 1993) recognized the glabrous or subglabrate forms native to North America as a distinct variety, var. glabrata; G. A. Mulligan (1996) did not accord such forms any taxonomic status. Glabrous and subglabrate forms occur in both Arabis eschscholtziana and A. pycnocarpa and sometimes even within a population that has moderately to densely pubescent forms. I support Mulligan’s view in not recognizing the glabrous forms as an infraspecific taxon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 261. | FNA vol. 7, p. 261. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | A. hirsuta subsp. eschscholtziana, A. hirsuta var. eschscholtziana, A. hirsuta var. glabrata, A. ovata var. glabrata, A. pycnocarpa var. glabrata, A. rupestris, A. stelleri var. eschscholtziana, Turritis spathulata | |
Name authority | R. M. Harper: Torreya 3: 88. (1903) | Andrzejowski: in C. F. von Ledebour, Fl. Altaica 3: 25. (1831) |
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