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FNA | Family List | FNA Vol. 7 | Brassicaceae | Arabis

3. Arabis pycnocarpa M. Hopkins, Rhodora. 39: 112, plate 458, figs. 1-3. 1937.

Arabis hirsuta (Linnaeus) Scopoli subsp. pycnocarpa (M. Hopkins) Hultén; A. hirsuta var. pycnocarpa (M. Hopkins) Rollins

Biennials or perennials; (caudex branched); usually densely hirsute (at least basally), rarely glabrescent, trichomes simple mixed with stalked or sessile, forked ones. Stems simple or several from base (rosette), erect, often branched distally, 1-8 dm, (pilose with trichomes appressed, malpighiaceous, or minutely stalked, forked, or hirsute basally with trichomes simple and minutely stalked, forked, sometimes almost exclusively pubescent with forked submalpighiaceous trichomes). Basal leaves: petiole 0.5-2 cm, (ciliate or not); blade spatulate, oblanceolate, or oblong, (0.8-)1.5-8 cm × (5-)10-25 mm, margins entire, repand, or dentate, apex obtuse or acute, surfaces sparsely to densely pubescent, trichomes sessile or stalked, simple or forked, and/or stellate. Cauline leaves (7-)10-45(-61), (overlapping or not); blade ovate to oblong or lanceolate, rarely linear, (1-)1.5-6(-8) cm × (1-)3-20(-25) mm, base subcordate or auriculate (auricles obtuse or subacute), margins dentate or entire, apex acute or obtuse, surfaces hirsute or adaxially glabrescent. Racemes often simple. Fruiting pedicels erect to erect-ascending, (2-)3-8(-12) mm (glabrous or sparsely pubescent). Flowers: sepals oblong, 2.5-4 × 0.5-1.5 mm, lateral pair not saccate basally; petals white, linear-oblanceolate or narrowly spatulate, 3.5-5(-5.5) × 1-2(-2.5) mm, apex obtuse; filaments 2.5-4 mm; anthers oblong, 0.7-1 mm. Fruits erect to erect-ascending, (often appressed to rachis), torulose, (3.5-)4-6(-6.5) cm × 0.8-1(-1.2) mm; valves each with obscure or somewhat prominent midvein extending to the middle; ovules (54-)60-86 per ovary; style (0.2-)0.5-1(-1.3) mm, (slender). Seeds narrowly winged throughout, oblong or suborbicular, (0.8-) 1-1.5(-1.7) × 0.8-1.3 mm; wing to 0.2 mm wide distally.

Varieties 2 (2 in the flora): North America, Asia.

1 Stems usually hirsute basally, rarely glabrescent, trichomes often simple, sometimes branched; basal leaf blades: surfaces with simple and stalked trichomes.   3a Arabis pycnocarpa var. pycnocarpa
+ Stems pilose, trichomes appressed, malpighiaceous, or minutely stalked, forked; basal leaf blades: surfaces with sessile, forked, and/or stellatetrichomes.   3b Arabis pycnocarpa var. adpressipilis

Lower Taxa


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