Braya Sternb. and Hoppe
Brassicaceae (Cruciferae), Draba family.
Denkschr. Bot. Ges. Regensb. 1:65. 1815.
Vegetative morphology. Plants perennial herbs; (1.2–)3.5–15(–22.7) cm high; caespitose; Low perenials that are mostly purple tinged herbs of tufted habit, with simple entire or slightly toothed leaves, white or purplish flowers and clyindrical, somewhat torulose silques. Taproot present. Caudex present. Ground-level or under-ground stems vertical and often branched. Vegetative, aerial, stem a small transition zone between roots and basal leaves, or vegetative stem a small transition zone between roots and branches arising at ground-level; aerial stems erect, or ascending, or decumbent, or prostrate; aerial stems glabrous, or sparsely hairy, or densely hairy; aerial stem hairs appressed, or spreading, or erect. Leaves in a basal tuft, or basal in a rosette. Leaves patent, or erect. Leaves alternate; simple; existing for a single season or less and marcescent (slighltly). Petioles present, or absent; 0–40 mm long (if applicable); winged (conspicuously so at the point of attachment), or unwinged; glabrous, or hairy; pilose; hairs more than the diameter of the petiole. Petioles hairs spreading. Leaf blade bases truncate, or attenuate. Blades (4–)10–40(–80) mm long; (0.3–)0.6–4(–6) mm wide. Blades appressed to the stem, or spreading; herbaceous, or somewhat fleshy; linear, or oblanceolate, or spatulate; appearing single-veined, or with inconspicuous veins. Blades adaxial surface dull (usually), or shiny; glabrous, or glabrescent, or hairy. Blades adaxial surface hairs pilose, or villous (if applicable); simple, unbranched, or branched (2 or 3 forked); sparse; white and translucent. Blades abaxial surface glabrous, or glabrescent, or hairy. Blades abaxial surface hairs sparse, or moderately dense (if applicable). Blades abaxial surface pilose (if applicable). Blades abaxial surface hairs white, or translucent hairs; curved (or forked); appressed, or spreading. Blade margins entire (usually), or dentate (slighlty, B. purpurascens); glabrous, or scabrous; with teeth on each side of the blade 1–2 (if applicable). Leaf apices acute, or obtuse, or rounded.
Reproductive morphology. Flowering stems present. Flowering stems conspicuously taller than the leaves (usually), or shorter than the leaves (B. thoridl-sulfii when stems are prostrate); without leaves (usually), or with leaves (and then only a single leaf); glabrous, or hairy. Flowering stem hairs pilose, or woolly; simple, or branched; white or translucent. Inflorescence head-like (in bud and in flower), or racemose (in fruit); dense (in flower), or diffuse (in fruit); elongating as the fruit matures; main axis hairy (trichomes stiffish). Pedicels glabrous, or with non-glandular hairs. Flowers per inflorescence 3–12; small, less than 5 mm in diameter or length; actinomorphic. Calyx sepals 4; free; (1.6–)2–3.5(–3.7) mm long; (0.7–)1–2 mm wide. Calyx green, or purple, or pink; herbaceous; glabrous, or hairy; pilose, or woolly. Calyx hairs white or translucent. Petals free; shorter than the calyx, or longer than the calyx; 4; white, or pink, or purple (tinged); without contrasting markings; obovate, or spatulate; unlobed; 2–4(–4.7) mm long; 1–3 mm wide. Stamens 6; filaments markedly unequal in length; free of the corolla; filaments glabrous. Anthers yellow; ovoid, or subglobose; 0.4–0.6 mm long. Gynoecia superior. Carpels syncarpous; 2. Ovaries pear-shaped, or ovate, or oblong; hairy; pilose, or woolly. Ovary hairs white, or translucent; spreading; straight, or wavy, or branched. Styles 1; completely fused; thick and short; 0.1–1 mm long. Stigmas per style 1; plate shaped, or receptive surface at the end of an otherwise unmodified style. Placentation parietal. Ovules 5–20. Fruit stalked; stalk (1–)2–5(–8) mm long. Fruit without calyx persisting; dry; a silique; ovoid, or elongate-cylindrical; not distinctly flattened; dehiscent. Fruit (3–)5–15(–17) mm long; 1.5–9 mm wide; yellowish, or purple, or green at maturity; hairy; surface venation ribbed, or appearing veinless. Seeds 5–20; 1–1.4 mm long; brown, or yellowish.
Chromosome information. 2n = 28, 56, 64, 84. Ploidy levels recorded 4x&8x&12X.
Notes. Harris (1985) considered Braya to be a natural group
with well-defined genetic boundaries. He revised the treatment of the genus for
North America based on studies of morphology (both traditional herbarium studies
and numerical analyses), cytology, ecology, and enzyme chemistry. recognizing
three sectons consisting of seven species and six varieties. The taxa relevant
to the eastern Canadian Arctic Archipelago are in two sections. Platypetalum
: B. glabella var. purpurascens of wide distribution in the
high arctic, B. glabella var. glabella of wide distribution in the
Arctic and sub-arctic and alpine regions B. glabella var.
prostrata, endemic to northern Ellesmere Island, B. thorild-wulffi
var. thorild-wulffi an endemic of Greenland and the northern Canadian
Arctic Archipelago; B. thorild-wulffi var. glabrata of Banks and
Victoria Island. Braya pilosa that was reported fromthe Mackenzie Delta
area is considered a fiction (Elven et all 2002). Section Sisymbriastrum
includes a single species, B. humilis with four varieties, var.
ellemerensis, an endemic of northern Ellesmere Island, var.
humilis widely distributed on calcareous soils in northern North America
; var. maccallae, endemic to the Rocky Mountains in southern Alberta and
British Columbia; and var. porsildii of the Rocky Mountains and MacKenzie
Mountains.
Harris (1985) provided the following key to the North American
sections of Braya.
1a. Stems leafy (usually 2 or more leaves per
stem); fruit a silique, linear, subclindrical, 9–33 times longer than
broad; seeds uniseriate..................2
1b. Stems scapose (occasionally
with a single leaf or leafy bract); fruit a silique or silicle, ovoid to
oblong-lanceolate, never liner, 1.25–8 times longer than broad, seeds
biseriate (except in B. longii and B. fernaldii)....
......................section Platypetalum
2a. Cauline leaves usually
3 or less per stem; basal leaves usually more than 20 times longer than broad;
fruiting inflorescence usually dense and crowded near top of stem; mature
siliques usually leass than 12 mm long, 9–10 times longer than
broad......section Braya
2b. Cauline leaves usually 3 or more per
stem; basal leaves usually less than 20 t imes longer than broad; fruiting
inflorescence rarely dense andusually scattered along the stem; mature siliques
often more than 12 mm long, 12–33 times longer than
broad...............section Sisymbriatrum
Harris (1985) provided the
following key to species of Braya in Section Platypetalum
(modified to include only taxa in the eastern Canadian Arctic Archipelago).
1a. Fruit a silicle, the length 1–2 times greater than the width; stems
erect and the petals longer than 4.7 mm or stems decumben to prostrate
and the petals shorter.... (Petals 2.0–3.7 mm long, 1.0–1.5 mm broad;
styel 0.25–0.75 mm long, stout; stems decumbent to prostrate; plants of
northern Greenland and northern and western Canadian Arctic Archipelago)...B.
thorild-wulffii
1b. Fruit a silique or long silicle, the length
2.5–8 times greater than the width; stems erect of ascending (rarely
decumbent to prostrate) and the petals mostly shorter than 4.7 mm..(
Siliques oval-elliptic to oblong-lancelolate; the margin of the septum expanded,
or not at all expanded, at the base, but never forming a sack-like pounch around
the lowermost seed; seeds few to several, arranged more or less in 2 rows)
...........B. glabella
Harris (1985) separated the two varieites of
B. humilis in the eastern Canadian Arctic Archipelago as follows.
1a.
Siliques 1.2–1.8 mm wide, not torulose; stems simple, becoming prostrate in
fruit; plants of northern Ellesmere Island... var. ellesmerensis
1b.
Siliques 0.6–1.1(-1.3) mm wide, usually more or less torulose; stems simple
or branches, ascending to erect; plants of various distributuions. (Flowers
small, average petal length less than 5 mm; most flowers developing normal
siliques; leaves often dentate or pinnatifid; plants of wide distribution in
North America. ...var. humilis.
Discussing phytogeogrpahy, Harris
(1985) noted that the present discontinuous distribution of Braya species
suggests that in pre-Pleistocene times they, or their ancestors, had a much more
continuous distribution across nothern North America. Glaciaiton removed
Braya from much of its former range and the genus has been only partially
successful in recolonizing these areas in post-glacial times. Part of this lack
of success has likely been due ot the absence of long distance dispersal
mechanism in Braya, but by far the most important factor has been the glacial
eradication of the edaphic conditions required by the genus from a large portion
of its fomrer range. Members of the genus are almost entirely, if not entirely
restricted to calcareous soild. Braya humilis is widely distributed on
sedimentary soils in western Canada and Alaska, but sompetely absent from the
granitic rock and soils of the eastern Canadian Shield.
Harris (1985) mapped
the distribution of B. humilis superimposed on the approximate limits of
the granitic bedrock of the eastern Canadian Shield and noted the
sharply-defined distribution limits of B..humilis in Ontario and Manitoba
attest to the inabliity of this species ot invade regions of granitic soils.
In order to explain the present-day distribution of Braya in North
America, it is necessary to postulate the survival of segments of the population
in unglaciated areas to the north and south of the ice-sheet as well as in
localized refugial areaqs that excaped glaciation even though surrounded by ice.
This 'genus' is in urgent need of a circumpolar biosystematic (and genetic)
treatment. The following major changes are here proposed as compared with
Petrovsky's draft: (a) The B. humilis group is separated as the genus
Neotorularia, see comment under that genus; (b) Braya glabella is
extended to include some related species and more should follow; (c) Braya
purpurascens is extended likewise; and (d) Braya pilosa is excluded.
Illustrations. • Genus Braya. Genus with green or purple-tinged herbs with a tufted habit, simple linear or narrowly spatulate, entire leaves, and small white or lilac flowers in head-like inflorescences.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
