Braya humilis subsp. maccallae
Braya humilis
dwarf braya, maccall's dwarf braya, mccalla's dwarf braya
alpine northern-rockcress, dwarf braya, low braya, low northern-rockcress
ascending to erect, often unbranched, 0.4–2.3 dm, moderately pubescent.
usually few to several from base, rarely simple, ascending or erect, rarely subdecumbent, (0.4–)0.8–2.5(–3.5) dm.
blade margins entire or, sometimes, sinuate-dentate, surfaces glabrescent to 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.
petals white, (4.4–)4.9–6.7(–7.2) × (2.1–)2.3–4(–4.2) 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).
often abortive, somewhat torulose, 0.7–1.2 mm wide when fully developed;
septum not fenestrate or split longitudinally.
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.
uniseriate, oblong, 0.6–0.9x 0.4–0.5 mm.
= 28.
Braya humilis subsp. maccallae
Braya humilis
Subspecies maccallae differs from subspp. elesmerensis and humilis in having leaf margins mostly entire, flowers exceptionally large, and a high percentage of abortive fruit. Cauline leaves are much reduced and arise from the base of the stem, giving an almost acaulescent appearance to the plant. Breeding studies (J. G. Harris 1985) indicate that subspp. maccallae and porsildii are self-incompatible, while most subspecies of Braya humilis are strongly autogamous.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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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