Flora of the Canadian Arctic Archipelago

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S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Braya humilis (C. A. Meyer) B. L. Robinson

Brassicaceae (Cruciferae), Draba family.

Published in In A.Gray, Syn. Fl. N. Amer. 1, 1: 141. 1895.

Type: Southern Siberia: Altai, in argillosis subsalsis ad fluvios Kenlyk, Kan, Jebagan; ad fluvium Tschuja, 1826, leg. Bunge. Holotype: LE: 1033.

Synonymy. Sisymbrium humile C.A. Meyer, in Ledeb., Icon. Pl. 2: 16, t. 147. 1830.

Torularia humilis (C.A. Meyer) O.E.Schulz, Feddes Repert. Beih. 12: 390. 1922.

Neotorularia humilis (C.A. Meyer) Hedge and J. Léonard, Bull. Jard. Bot. Nat. Belg. 56: 394. 1986. .

Pilosella novae-angliae Rydberg, Torreya 7: 158. 1907.

Pilosella richardsoniii Rydberg, Torreya 7: 159. 1907.

Arabidopsis novae-angliae (Rydberg) Britton, Britton and Brown, d. 2 ed. 2, 2: 176 (fig. 2064). 1913.

Torularia humilis (C.A.Meyer) O.E.Schulz subsp. arctica Böcher, Meddel. Grønland 147, 7: 29. 1950.

Braya novae-angliae (Rydberg) T.J. Sørensen subsp. ventosa (Rollins) Böcher,

Braya novae-angliae (Rydberg) T.J. Sørensen var. interior Böcher, Meddel. Gronland 124(7): 20. 1956.

Braya novae-angliae (Rydberg) T.J. Sørensen var. interior Böcher, f. capitata Böcher, Meddel. Gronl. 124(7): 20. 1956.

Braya novae-angliae (Rydberg) T.J. Sørensen var. laurentiana Böcher, Meddel. Gronl. 124(7): 19. 1956.

Braya richardsonii (Rydberg) Fernald, Rhodora 20: 203. 1918.

Braya intermedia T.J.Sørensen, Meddel. Grønl. 136, 8: 15. 1954.

Braya richardsonii (Rydb.) Fernald, Rhodora 20: 203. 1918.

Braya humilis (C.A.Meyer) B.L. Rob. subsp. arctica (Böcher) Rollins, Rhodora 55: 109. 1953.

Torularia arctica (Böcher) Á. Löve and D. Löve, Bot. Not. 128: 513. 1976.

Braya humilis B.L. Rob. subsp. arctica (Böcher) Rollins, f. biloba Böcher, Rhodora Meddel. Gronl. 55: 115. 1953.

Braya humilis B.L. Rob. var. arctica ( Böcher ) B. Boivin, Phytologia 18: 285. 1969.

Braya humilis (C.A.Mey.) B.L. Rob. subsp. richardsonii (Rydberg) Hultén, Ark. Bot., n. s., 7, 1: 66. 1968a.

Torularia richardsonii (Rydb.) Á. Löve and D. Löve, Bot. Not. 128: 513. 1976.

Braya humilis B.L. Rob. subsp. ventosa Rollins, Rhodora 55: 114. 1954.

Braya humilis B.L. Rob. var. ventosa (Rollins) B. Boivin, Phytologia 16: 300. 1968.

Braya humilis B.L. Rob. var. abbei (Böcher) B. Boivin, Phytologia 16: 299. 1968.

Braya humilis B.L. Rob. var. americana (Hooker) B. Boivin, Phytologia 16: 300. 1968.

Braya humilis var. interior (Böcher) B. Boivin, Phytologia 16: 300. 1968.

Braya humilis var. laurentiana (Böcher) B. Boivin, Phytologia 16: 300. 1968.

Braya humilis var. leiocarpa (Trautv.) Fernald, Rhodora 39: 276. 1937.

Braya humilis var. novae-angliae (Rydberg) Fernald, Rhodora 20: 201. 1919.

Braya novae-angliae (Rydberg) T.J. Sørensen, Meddel. Grønland 136, 8: 22. 1954.

Vegetative morphology. Plants 5–20(–33) cm high; perennial herbs (rarely biennial); caespitose. Taproot present. Ground level or underground stems vertical. Caudex present. Aerial stems branching from a tap at or near ground level into two or more branches, or developed; erect, or ascending, or prostrate (rarely). Aerial stem trichomes spreading, or erect (simple, 2-forked, or 3-forked). Leaves mainly basal and distributed along the stems; erect (spreading); alternate; dying annually and non-persistent. Petioles absent (usually), or present (larger, older leaves); 7–9 mm long (if applicable); not winged. Leaf blades simple. Leaf blade bases attenuate. Leaves not grass-like. Blades 5–42(–55) mm long, (0.4–)0.8–9 mm wide (at widest point; basal leaves, green to deep purple), appressed to the stem or spreading, oblanceolate (sometimes broadly so), appearing single-veined. Blade adaxial surface dull, without sessile glands, hairy, hairs villous, hairs simple or branched (2- or 3-forked hairs), hairs sparse to dense, hairs white, or translucent. Blade abaxial surface hairy, hairs villous, hairs sparse or moderately dense, hairs white, hairs curved (or forked), hairs appressed or spreading. Blade margins entire and dentate (entire, sinuate-dentate, or shallowly pinnatifid (rarely)), with non-glandular hairs or glabrous (ciliate, especially at base), with 0–3 teeth on each side of the blade, with teeth toward the base; apices obtuse.

Reproductive morphology. Flowering stems two or more per plant; with leaves (3–10 similar to the basal leaves, but reduced upward, often purple or purple-tinged; this species is conspicuously different from other members of the genus Braya that are scapose or with only one leaf). Flowering stems hairy. Flowering stems woolly. Flowering stem hairs simple, or branched (2- or 3-forked); white or translucent. Inflorescences head-like (in flower), or racemose, or head-like (in fruit); dense (in flower), or diffuse (in fruit.); elongating as the fruit matures. Pedicels with non-glandular hairs. Flowers per inflorescence 10–15; small. Sepals conventional; 4; free; 0.6–1.8 mm long; (1.5–)1.8–3.1(–3.6) mm wide; green, or purple; herbaceous. Calyx hairy (moderately so, or sometimes glabrescent). Calyx hairs pubescent, or woolly (with forked, rarely simple trichomes); white or translucent. Calyx margins ciliate (sometimes, as a tuft of hairs at the tip). Petals conventional; free; 4; white, or purple (tinged); obovate, or oblanceolate; unlobed; (2.5–)3–5(–7.5) mm long; (0.7–)0.9–4(–4.2) mm wide. Stamens 6; stamen filaments markedly unequal in length; stamen filaments glabrous. Anthers yellow; sub-globose; 0.5–0.9 mm long. Ovary superior; carpels 2; syncarpous. Ovaries oblong; hairy; villous. Ovary hairs moderately dense; white; appressed, or spreading; wavy, or branched (bifid). Styles 1; completely fused; thick and short; 0.2–1.4(–1.7) mm long. Stigmas per ovary 1. Placentation parietal. Ovules per ovary 30–40. Fruit stalked; stalk 3–5 mm long; dry; a silique; elongate-cylindrical (linear, subcylindrical, or lsigtly compressed parallel to the septum, very torulose to not at all torulose, curved or straight; much longer than wide); yellowish, or green at maturity; (7.5–)9–29 mm long; (0.6–)1.2–2 mm wide; hairy, or glabrescent; surface venation ribbed (longitudinally); not distinctly flattened; dehiscent; shedding the outer walls to expose a thin inner wall, with the seeds attached at the margins on either side. Styles persisting in fruit (0.2–)0.5–1.4(–1.7) mm long. Seeds 15–30(–40); (0.7–)1.2–1.3 mm long (0.3–0.75 mm wide); yellowish, or brown; surfaces smooth (rugose at 40×).

Chromosome information. 2n = 28–56.

2n = 28 (4x). Mulligan (1965b, 'humilis');

2n = 30. Zhukova et al. (1973, northeastern Asia, 'humilis'); Mulligan (2003);

2n = 40. Rollins (1953, western Alaska, Kuskokwim area, 'humilis');

2n = 42 (6x). Mulligan (1965b, 2003, 'humilis');

2n = 56 (8x). Mulligan (1965b, 2003, 'humilis').

Ploidy levels recorded 4x/6x/8x.

Ecology and habitat. Substrates: flood plains (disturbed sites); dry, moderately well-drained areas; gravel, sand; calcareous. Calcareous soils and gravels on river, lake and sea shores, moraines, solifluction lobes, and disturbed sites.

North American distribution. Elven (personal communicaton, 2005) noted that species occurs in open, naturally or artificially disturbed sites, almost always calcareous, and dry. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands. Range in the Canadian Arctic Archipelago limited. Uncommon. Low Arctic (Alaska east to Great Bear Lake, south through the Rocky Mountains to Colorado, north through the western Canadian Arctic Archipelago in isolated locations to northern Ellesmere Island; isolated populations in western and eastern Greenland, Hudson Bay, Newfoundland, Anticosti Island, Vermont, and the north shore of Lake Superior.). Arctic islands: Parry islands (Eglinton), Banks, Victoria.

Northern hemisphere distribution. Amphi-Beringian, or North American. Taimyr – Severnaya Zemlya, Anabar–Olenyok, Kharaulakh, West Chukotka, East Chukotka, West Alaska, North Alaska – Yukon, Central Canada, Labrador – Hudson Bay, Ellesmere Land – Peary Land, East Greenland.

General notes. Harris (1985) separated the two varieties of B. humilis in the 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 distributions. 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

Braya humilis is widely distributed on sedimentary soils in western Canada and Alaska, but completely absent from the granitic rock and soils of the Canadian Shield. 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 localised refugial areas that escaped glaciation even though surrounded by ice.

Harris (1985) superimposed the distribution of B. humilis on the map, showing the approximate limits of the granitic bedrock in the eastern Canadian Shield. He noted the sharply defined distribution limits of B. humilis in Ontario and Manitoba and suggested that this indicated the inability of this species to invade regions of granitic soils.

Acceptance of Neotorularia, as distinct from Braya, was proposed in the work of Hedge and Léonard, in Léonard (1986) and Al-Shehbaz et al. (1999), Novon 9: 296–307. In an arctic context, it consists of entities within what has been named Braya humilis and 1–2 close relatives, entities accepted by Rollins (1993) within his concept of B. humilis.

The genus name Torularia (Coss.) O.E. Schulz was proposed conserved for this genus [Taxon 31: 754, 1982], but this proposal was rejected [see Taxon 34: 661, 1985]. More recent DNA evidence has suggested that B. humilis belongs with other Braya species, and it is to be so treated in the Flora of North America treatment (Al-Shehbaz, personal communication, Dec. 2003).

The writing of Harris (1985) on this taxon noted that the plants have a tendency to form small populations of fairly uniform individuals, which are each somewhat different from the next population, but may be quite similar to some distant populations. He thought this may be due to several factors, suggesting the following:

1. Hexaploid populations probably often arise through hybridisation of tetraploid and octoploid populations. It appeared to Harris (1985) that hybridisation in different areas may have produced hexaploids which bear some morphological characteristics attributable to ploidy level. Mulligan (1965) noted that hexaploids are more variable than tetraploids and octoploids in style length, pod size, and life span, but most often differences in chromosome number are not accompanied by obvious morphological differences.

2. Some morphological similarities between distant populations may be caused by the establishment of one or a few individuals and subsequent inbreeding of similar alleles in different populations that become fixed. Although this may account for some long-distance interpopulation similarities, paradoxically, it is probably this same process of genetic depletion and fixation, postulated and demonstrated in many groups of flowering plants (Stebbins 1942, 1957, Solbrig 1972, Soltis 1982), that is most responsible for the distinctiveness of many B. humilis populations.

Braya humilis forms a highly variable polyploid complex that has confounded generations of botanists. The long list of synonyms attests to the taxonomic difficulties in the group. In the Canadian Arctic Archipelago, however, most populations fall comfortably within a broad concept of B. humilis. One exception are populations with prostrate to decumbent stems, exceptionally wide siliques, and fenestrate septae from northern Ellesmere Island that may deserve infraspecific recognition (Harris 2004).

Illustrations. • Herbarium specimen. Fruiting plant collected N.W.T., Richards Island. 29 July - 5 August, 1947. A.E. Porsild 16826. CAN 64195. • Arctic Island Distribution.


This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.

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