Saxifraga rivularis L.
Alpine brook saxifrage.
Saxifragaceae, saxifrage family.
Sp. Pl. 1: 404. 1752.
Type: Sweden (Lapland). Stockholm Linnaean Herbarium 174.5 (S) lectotype, selected by Webb, Bot. J. Linn. Soc. 95: 264. 1987.
Saxifraga debilis Engelm. ex Gray
Saxifraga hyperborea R.
Br. subsp. debilis (Engelm. ex Gray) A. and D. Löve and Kapoor
Saxifraga rivularis var. debilis (Engelm. ex Gray) Dorn
Saxifraga rivularis var. flexuosa (Sternb.) Engl. and Irmsch.
Saxifraga rivularis forma purpurascens Lange
Vegetative morphology. Plants perennial herbs (dwarf delicate plants); 2–12 cm high; not caespitose (loosely tufted); loosely tufted with divergent branches at ground-level; petiolles long; flowering stems not elongating much above the leaves; vegetatively proliferating by bulbils or fragmentation (basal bulbils consisting of a few thick scale leaves), or not vegetatively proliferating by bulbils or fragmentation. Caudex absent. Ground-level or under-ground stems horizontal, or not developed horizontally or vertically (on some herbarium specimens); stoloniferous (as horizontally growing "runners", to 6 cm long, with glandular hairs on the surface, and with scale leaves. The runners bend upwards, producing roots and foliage leaves), or rhizomatous (as an abbreviated, vertical rhizome, sometimes not readily visible); elongate, or compact. Leaves not heterophyllous; in a basal tuft; alternate; simple; existing for a single season or less. Petioles (15–)20–40(–50) mm long; glabrous, or hairy (especially on the margins at the flared base); pilose (if applicable); hairs less than the diameter of the petiole. Leaf blade bases cuneate (usually), or truncate. Blades 2–10 mm long; 3–14 mm wide (leaves on average larger than those in S. hyperborea). Blades triangular (inverted); flat; veins palmate, or with inconspicuous veins. Blades adaxial surface glabrous. Blades abaxial surface glabrous. Blade margins lobed (with 3 very often 5, and sometimes 7 lobes). Blade margins glabrous; degree of incision 50–70 %. Conspicuous hydathodes present (at the apex of each leaf lobe, but easily overlooked). Leaf apices acute.
Reproductive morphology. Flowering stems present. Flowering stems about as high as the leaves; with leaves (often conspiously large and lobed leaves near the flowers); hairy. Flowering stem hairs pilose. Flowering stems glandular hairs present. Flowering stem hairs longer than the diameter of the flowering stem; white or translucent (with limited brown or purple spots of pigmentation). Flowers solitary, or in inflorescences. Inflorescence paniculate (if applicable). Pedicels present; with glandular hairs. Flowers per inflorescence 1–2; small, less than 5 mm in diameter or length, or medium-sized, 5–15 mm in diameter or length. Calyx sepals 5; free; 2.5–3.5 mm long; 1.2–2.2 mm wide. Calyx green; without sessile glands; glabrous (hypanthium hairy). Petals free; longer than the calyx; 5; white, or pink; obovate, or elliptic (narrow); unlobed; 3.5–4.5 mm long; 1–2 mm wide. Stamens 10. Anthers 0.2–0.4 mm long. Nectaries present. Receptacle 2.5–3.5 mm high. Gynoecia partly inferior. Carpels partly fused; 2. Ovaries glabrous. Styles absent (stigmas preseent at the top of each carpel). Stigmas per style 1; plate shaped. Placentation axile. Ovules numerous. Fruit with calyx persisting; dry; a capsule; urceolate; dehiscent; splitting to the base into separate segments. Fruit 5–7.5 mm long; 2–4 mm wide; brown, or straw coloured; glabrous; surface venation ribbed. Seeds numerous; 0.5–0.6 mm long; brown; with surfaces smooth.
Chromosome information. 2n = 50, 52, and 56. 50-52-56
(4x). - Böcher (1938a Greenland?, 2&#;n&#;none = 56);
Sørensen and Westergaard in Löve and Löve (1948 Greenland);
Löve and Löve (1951, 1956b Iceland, 1965 North America, 1982a arctic
Canada); Jørgensen et al. (1958 Greenland); Engelskjøn and Knaben
(1971 northern and arctic Norway, 2n = 50–52 51–53 52);
Engelskjøn (1979 southern Norway, 2n = 50–52, Bear Island,
2n = 52, 3 counts); Borgen and Elven (1983 northern Norway).
The
following tetraploid chromosome counts from the amphi-Beringian area have been
preliminarily excluded; they may belong to S. arctolitoralis or a
relative: Zhukova (1968 north eastern Asi), Zhukova and Tikhonova (1971,
2n = 52, 1973 Chukotka, 2n = 48), and Packer and McPherson (1974
northern Alaska, Point Barrow). A count from western North America (Rocky Mts)
may belong to S. rivularis: Löve et al. (1971). These counts,
together with those of S. arctolitoralis from the Asian side, might
indicate the presence of an arctic amphi-Beringian tetraploid that should be
critically compared with both S. rivularis and S. hyperborea.
Ploidy levels recorded 4x.
Distribution. Northern hemisphere distribution: circumpolar. Arctic, or alpine. Range in the Canadian Arctic Archipelago widespread. Common. Arctic Islands: Baffin, Devon, Ellesmere, Coats.
Ecology and habitat. Substrates: wet meadows, along streams, lake shores; imperfectly drained moist areas, or on seepage slopes (gravely, and mossy places, or wet slopes); calcareous, or nitrophilous (found below bird cliffs and near human habitations. Described as "markedly calcifugous", Polunin 1940); sand, clay, moss; with high organic content, or peat.
Notes. Polunin (1940) indicated that this is one of the most
ubiquitous and generally common of arctic plants. It varies considerably in
height, hairiness, and the colour of the petals. On these characters minor
formas have been recognized, but they were not maintained by Porsild (1964) or
Porsild and Cody (1980).
Polunin (1940) noted that this plant may penetrate
farther into very late melting snow patches than any other angiosperm. It is
frequent almost everywhere, and in places rather abundant, although so small as
to be often overlooked.
Porsild (1964) indicated that plants completely
matching the description of S. hyperborea commonly grow within clones of
typical S. rivularis and although the chromosome counts are different,
(S. hyperborea 2n = 26, S. rivularis 2n =52) he
implied that S. hyperborea is merely an unimportant, ecological
variation, presumably an autoploid.
A hybrid with S. rivularis as the
maternal parent and S. cernua named S. Svalbardensis has been
described from Svalbard. Molecular evidence, (Brochmann et al. 1998) indicated
that the hybridization event possibly occurred only a single time. The data from
this study also suggest that the diploid S. hyperborea is a progenitor of
the tetraploid S. rivularis.
This is an Amphi-Atlantic arctic
species, that prviously included S. hyperborea. At present, only plants
with stolons and 2n = 52 are attributed to S. rivularis. However,
the distinctiveness of the growth forms and other morphological distinctions
between S. rivularis and S. hyperborea are not always obvious.
(Zhmylev in Elven et al. 2003).
Illustrations. • Habitat. Loosely clustered plant growing in moist moss. Nunavut, Baffin Island, Pond Inlet, under the staircase of the Renewable Resources Building. L.J. Gillespie, 6042. CAN. • Habit. ALPINE BROOK SAXIFRAGE Close-up of plant showing leaves have deeply lobed blades that tapper into the petioles and flowers with five free petals and yellow anthers. Nunavut, Baffin Island, Pond Inlet, under the staircase of the Renewable Resources Building. L. Gillespie, 6042. CAN. • Climbing plant. Plant groiwng in moss in the shelter of a barrel. Note that the flowering stems have elongated and are approaching 50 cm high. J.M. Gillett 19011. CAN. • Plant haabit - Baffin Island. Plants growing on rocky ground. Nunavut, Baffin Island, Cape Raper : 69° N 44.140', 67 degrees 07.672' W. Photograph by Sherry Sadler. Identification Marte Horton Jorgenson. • Plant habit - Baffin Island. Plants growing on rocky ground. Nunavut, Baffin Island, Cape Raper : 69° N 44.140', 67 degrees 07.672' W. Photograph by Sherry Sadler. Identification Marte Horton Jorgenson. • Leaf shape. Leaves vary in shape from unlobed to 3 or 5-lobed (arrow). they appear glabrous at a distance, but close-up are seen to have a few glandular hairs. The flowers have five white petals with a tinge of pink towards the base, 10 stamens, and two green carpels topped with white stigmas. Nunavut, Baffin Island, Pond Inlet, under the staircase of the Renewable Resources Building. L.J. Gillespie, 6042. CAN. • Close-up of flowers. Another view of the flowers that have five white petals with a tinge of pink towards the base, 10 stamens, and two green carpels topped with white stigmas. Nunavut, Baffin Island, Pond Inlet, under the staircase of the Renewable Resources Building. L.J. Gillespie, 6042. CAN. • Arctic Island Distribution.
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).
