Braya humilis
Braya humilis subsp. humilis
alpine northern-rockcress, dwarf braya, low braya, low northern-rockcress
dwarf braya
usually few to several from base, rarely simple, ascending or erect, rarely subdecumbent, (0.4–)0.8–2.5(–3.5) dm.
ascending to erect, branched or unbranched, 0.4–3.3 dm, sparsely to moderately pubescent.
blade margins sinuate-dentate, shallowly pinnatifid, or entire, surfaces moderately pubescent.
blade obovate, spatulate, oblanceolate, oblong, or sublinear, (0.3–)0.5–2(–3.5) cm × 1–8(–10) mm, base attenuate or cuneate, margins entire, sinuate-dentate, or pinnatifid, apex acute or obtuse, (surfaces sparsely to densely pubescent or, rarely, glabrous).
3 or more;
blade similar to basal, smaller distally, distalmost sessile or subsessile. (Racemes bracteate proximally, very rarely throughout, elongated in fruit.) Fruiting pedicels erect, ascending, or divaricate, (2.5–)3–8(–12) mm.
sepals 2–3 × 0.8–1.2 mm, (sometimes slightly saccate basally);
petals white, pink, or purple, (broadly obovate or spatulate), 3–5(–8) × (1–)1.5–2.5(–4) mm, (apex rounded);
filaments 2–3(–4) mm;
anthers oblong, 0.4–0.7mm, (apex apiculate).
petals white, pink, or purple, 2.5–6.9(–7.5) × (0.7–)0.9–4(–4.2) mm.
linear, torulose or not, (mostly straight), (0.9–)1.2–2.5(–3.2) cm × 0.6–1.8(–2) mm (uniform in width);
valves pubescent or, rarely, glabrescent, trichomes submalpighiaceous, rarely mixed with fewer, simple ones;
septum fenestrate or not;
ovules 20–44 per ovary;
style 0.3–0.8(–1) mm;
stigma entire or strongly 2–lobed.
usually fertile and fully developed, somewhat torulose, 0.6–1.2(–1.3) mm wide;
septum not fenestrate or split longitudinally.
uniseriate, oblong, 0.6–0.9x 0.4–0.5 mm.
= 28, 42, 56, 70.
Braya humilis
Braya humilis subsp. humilis
Subspecies 4 (4 in the flora).
Braya humilis was recognized in Asian floristic accounts as a member of Neotorularia Hedge & J. Léonard (= Torularia O. E. Schulz), but molecular studies (S. I. Warwick et al. 2004) clearly support its assignment to Braya, as done by all North American authors (e.g., M. L. Fernald 1918; E. C. Abbe 1948; T. W. Böcher 1956, 1973; J. G. Harris 1985; R. C. Rollins 1993). The species is highly variable in leaf shape and margin, flower size and color, pubescence, fruit length and orientation, chromosome number, and length of the bracteate portion of the raceme. Occurrence of “races” with various ploidy levels is one of the reasons for variability that led to recognition of infraspecific taxa. The synonymy below pertains only to North America, with nearly as many names given to the Asian variants. Numerous morphological extremes were described in North America, Russia, and China, but most of those represent only part of an otherwise continuous variation. For example, fully bracteate racemes, though rare, appear sporadically in populations that otherwise have racemes only basally bracteate. Three morphological forms are more sharply distinct from the general subsp. humilis amalgam and seem to have some biological significance. All of them are restricted to areas in or near regions believed to have served as glacial refugia during the Pleistocene. They are recognized here as additional subspecies.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies humilis is extremely variable morphologically. In a general way, morphological form correlates with ploidy level, e.g., tetraploids, octoploids, and decaploids tend to be short in stature with small leaves. Hexaploids are less predictable. They range from short plants with small leaves to large, robust, multi-branched plants with large, pinnatifid leaves. Attempting to segregate most morphological forms of Braya humilis into logical infraspecific taxa is an exercise in futility. Populations that appear distinctive in the field almost always blur imperceptibly into the larger subsp. humilis continuum when compared with other populations from across the range of distribution. Subspecies humilis is broadly distributed on calcareous substrates in arctic, subarctic, alpine, and boreal regions of North America and Asia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Fruits (1-)1.2-1.8(-2) mm wide, not or weakly torulose; stems unbranched, ascending (prostrate in fruit). | subsp. ellesmerensis |
1. Fruits 0.6-1.2(-1.3) mm wide, usually somewhat torulose; stems unbranched or branched, ascending to erect | → 2 |
2. Petals 2.5-6.9(-7.5) mm; fruits usually fertile and fully developed; leaf blade margins often sinuate-dentate, pinnatifid, or entire. | subsp. humilis |
2. Petals (4.4-)4.9-6.9(-7.2) mm; fruits often abortive; leaf blade margins entire or sinuate-dentate, not pinnatifid | → 3 |
3. Leaves and stems glabrescent or moderately pubescent. | subsp. maccallae |
3. Leaves and stems densely pubescent. | subsp. porsildii |
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