Saxifragaceae A.L. de Jussieu
Saxifrage family.
Saxifragaceae, saxifrage family.
Vegetative morphology. Plants perennial herbs; 1–30 cm high (mean 10 cm); caespitose, or not caespitose; with single unbranched stems, or with erect unbranched stems arising close together, or cushion-like, or with branched or unbranched matted stems; vegetatively proliferating by bulbils or fragmentation, or not vegetatively proliferating by bulbils or fragmentation. Taproot present (occasionally, S. serpyllifolia, S. tricuspidata), or absent (usually). Caudex present, or absent. Ground-level or under-ground stems horizontal, or not developed horizontally or vertically (usually); stoloniferous (S. flagellaris), or rhizomatous (Chrysosplenium, S. rivularis); elongate, or compact. Aerial stems erect, or decumbent (less commonly); glabrous, or sparsely hairy, or densely hairy. Leaves heterophyllous (varying between the basal leaves and leaves on the flowering stems), or not heterophyllous; basal in a rosette, or in a basal tuft, or distributed along the stems; alternate (usually), or opposite (S. oppositifolia); simple; evergreen, or existing for a single season or less, or marcescent. Petioles absent, or present; 0–50 mm long (mean 14 mm); glabrous, or hairy; puberulent, or pilose, or villous. Leaf blade bases cordate, or truncate, or obtuse, or acute, or cuneate, or attenuate. Blades 2–70 mm long (mean 13 mm); 0.4–35 mm wide (mean 7 mm). Blades herbaceous, or leathery, or succulent; elliptic, or linear, or lanceolate, or oblanceolate, or oblong, or ovate, or obovate, or circular, or spatulate; flat; veins pinnate (usually), or veins palmate (Chrysosplenium, Saxifraga cernua and S. rivularis). Blades adaxial surface glabrous, or hairy. Blades adaxial surface hairs glandular (usually). Blades abaxial surface glabrous, or glabrescent. Blade margins lobed, or not lobed. Blade margins with non-glandular hairs, or glabrous. Conspicuous hydathodes present, or absent. Leaf apices acute, or obtuse, or acuminate, or rounded.
Reproductive morphology. Plants monoecious (S. eschscholtzii), or bisexual. Flowering stems present. Flowering stems without leaves, or with leaves; hairy (usually), or glabrous. Flowers solitary, or in inflorescences. Inflorescence spicate, or racemose, or paniculate, or cymose, or head-like; terminal, or axillary; 0–3 cm long; with bulbils, or without bulbils. Pedicels present, or absent. Flowers per inflorescence 1–15; small, less than 5 mm in diameter or length, or medium-sized, 5–15 mm in diameter or length; actinomorphic. Calyx sepals 4 (rarely), or 5 (usually); free. Calyx green (usually), or yellow, or purple, or red; hairy, or glabrous. Petals free; same length as the calyx, or longer than the calyx (more commonly); 5; green, or white, or yellow, or red, or pink, or purple; with contrasting markings, or without contrasting markings; elliptic, or ovate, or obovate, or lanceolate, or oblanceolate, or spatulate; unlobed; 1–12 mm long (mean 5 mm). Flowers unisexual, or bisexual. Stamens 4–10 (4–8 Chrysosplenium, 5 stamens plus 5 staminoidia, Parnassia, 10 stamens, Saxifraga 10 stamens); filaments all equal in length; free of the corolla. Gynoecia superior, or partly inferior, or inferior. Carpels syncarpous, or partly fused; 2 (usually), or 4 (Parnassia). Ovaries glabrous, or hairy. Styles 2; free. Stigmas per style 2–4. Placentation axile. Ovules 25–120. Fruit with calyx persisting (usually), or without calyx persisting; dry; a capsule; spherical, or ellipsoid, or ovoid; dehiscent; splitting to the base into separate segments. Fruit 0.3–12 mm long (mean 6 mm); 2–12 mm wide (mean 5 mm); black, or brown, or purple, or green at maturity; hairy (rarely), or glabrous (usually). Seeds 25–50; 0.5–6 mm long (mean 1.3 mm); brown, or yellowish; with surfaces smooth, or verrucose, or ridged, or winged.
Distribution. Northern hemisphere distribution: circumpolar (commonly), or amphi-Atlantic, or amphi-Beringian, or North American. Arctic, or low arctic, or alpine. Range in the Canadian Arctic Archipelago widespread. Common, or rare, or uncommon.
Ecology and habitat. Substrates: acidic (rarely), or calcareous (commonly), or nitrophilous.
Notes. Warming (1909) documented five growth-forms among Arctic
Saxifragaceae.
1. Species with leaves in a rosette: S.
hieracifolia and S. nivalis. These species he considered to have a
vertical rhizome. The primary root dies early and numerous adventitious roots
develop. New shoots develop in the axils of the upper leaves.
2. Species
with vertical rhizomes, foliage leaves in a loose rosette, bulbils or runners
with scale leaves or reduced foliage leaves, and adventitious roots:
Chrysosplenium, S. cernua, S. hirculus, and S. rivularis.
3.
Species in which the main stem is vertical and bears a close rosette of leaves
and many adventitious roots. The stem dies away completely after flowering.
Lateral shoots arise from the leaf-axils in no fixed order and develop more or
less horizontally along the ground for some distance, terminating in a new
rosette, e.g. S. paniculata and S. flagellaris.
4. Species
with a many headed rhizome and a primary root that remains alive for a long
time. Adventitious roots are few in number, and vegetative propagation is by
lateral shoots becoming independent: S. cespitosa and S.
tricuspidata.
5. Creeping herb species in which the shoots are prostrate
and have their internodes more or less elongated, with a primary root that
appears to be able to live several years: S. eschscholtzii, S.
oppositifolia, and S. aizoides.
The following species have been
noted as evergreen but not to the same extent: S. aizoides, S.
aizoon, S. cespitosa, S. hieracifolia, S. nivalis,
S. oppositifolia, and S. tricuspidata. Old dead leaves persist for
a long time especially on those species that belong to dry habitats, e.g., S.
cespitosa, S. hieracifolia, S. nivalis, and S. oppositifolia.
Flowers develop the year previous to that in which they open in S.
cespitosa, S. hieracifolia, S. nivalis, S.
oppositifolia, S. rivularis, and possibly all species. Staminate
flowers occur rarely in S. oppositifolia, but pistillate flowers, which
are smaller than the hermaphroditic ones, appear to be common in several
species. Stamens are present, but smaller than usual and not fully developed.
Normal flowers have ten anthers and two carpels, but other numbers have been
observed, for example, 6 and 7-merous gynoecia in S. cernua. Tri-merous
gynoecia have been found in S. aizoides, S. cespitosa and S.
tricuspidata, and 4- and 5-merous in S. oppositifolia. The flowers
have nectar secreted at the base of the gynoecium, and in some instances scent
has been noted. Protandy, the maturation of the stamens before the stigmas, has
been observed in Chrysosplenium, S. aizoides, S.
paniculata, S. cespitosa, S. cernua, S. hieracifolia,
S. hirculus, S. nivalis, S. rivularis, and S.
tricuspidata. Protogyny, the ripening of the stigmas before the anthers,
occurs in S. cernua, S. cespitosa, S. hieracifolia, and S.
nivalis, but only slightly. However, S. oppositifolia is distinctly
protogynous. Self pollination is uncommon, but may occur when anthers touch
stigmas. Fruit set and seed formation is common in many species. Seed ripens, in
most species but possibly not every year in every locality. Those that do not
set seed at all, or do so rarely, are S. cernua and S. rivularis
that primarily propagate vegetatively. How common fruit-setting is in S.
foliolosa, S. flagellaris and S. hirculus requires further
investigation.
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).