Saxifragaceae A.L. de Jussieu
Saxifrage family.
Plants herbs; perennial herbs; with single unbranched stems, or with erect unbranched stems arising close together, or cushion-like, or with branched or unbranched matted stems; 1–30 cm high (mean 10 cm); vegetatively proliferating by bulbils not in the inflorescence, or not vegetatively proliferating by bulbils; without milky juice; not glandular viscid. Taproot present (occasionally, S. serpyllifolia, S. tricuspidata), or absent (usually). Ground level or underground 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); not conspicuously jointed; not filiform; glabrous, or sparsely hairy, or densely hairy. Branches not glaucous; epidermis not flaky. Leaves all basal in a rosette, or mostly basal, or distributed along the stems; alternate (usually), or opposite (S. oppositifolia); not distinctly distichous; simple; heterophyllous (varying between the basal leaves and leaves on the flowering stems), or not heterophyllous; evergreen, or deciduous, or marcescent. Stipules absent, or present; scale-like; not sheathing. Petioles absent, or present; 0–50 mm long (mean 14 mm). Blades 2–70 cm long (mean 13 mm); 0.4–35 mm wide (mean 7 mm); herbaceous, or leathery, or succulent; elliptic, or linear, or lanceolate, or oblanceolate, or oblong, or ovate, or obovate, or circular, or spatulate; without auricles; flat; with pinnate veins (usually), or with palmate veins (Chrysosplenium, Saxifraga cernua and S. rivularis); not septate nodulose; glabrous (usually), or hairy; with hairs on the adaxial surface only, or with hairs on the abaxial surface only, or with hairs equally dense on both surfaces. Hairs on blades glandular (usually). Blades adaxial surface dull. Leaf bases cordate, or truncate, or obtuse, or acute, or cuneate, or attenuate. Leaves lobed, or not lobed. Leaf margins entire; with non-glandular hairs, or glabrous. Conspicuous hydathodes present, or absent. Leaf apices acute, or obtuse, or acuminate, or rounded.
Forming flowers and fruit. Plants monoecious (S. eschscholtzii), or bisexual. Flowering stems 0.5–18 cm long (mean 6 cm); without leaves, or with leaves; hairy (usually), or glabrous. Flowering culm nodes not rooting at the lower nodes. Flag leaf sheaths not inflated. Leaf or reduced bract closely associated with the base of the inflorescence without calloused tip. 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. Bisexual spike(s) without empty bracts at the base. Inflorescence without involucral bracts. Flowers per inflorescence 1–15; small, less than 5 mm in diameter or length, or medium-sized, 5–15 mm in diameter or length; unisexual, or bisexual; actinomorphic. Floral scales not reflexed; not falling early. Callus not differentiated. Perianth present. Calyx present; sepals 4 (rarely), or 5 (usually); sepals free; green (usually), or yellow, or purple, or red; herbaceous; hairy, or glabrous; non-accrescent. Petals present; 5; free; 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; not tipped with an awn-like bristle; 1–12 mm long (mean 5 mm); not spurred; same length as the calyx, or longer than the calyx (more commonly). 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. Nectaries in bisexual flowers absent. Carpels syncarpous, or partly fused; 2 (usually), or 4 (Parnasia). Gynoecia superior, or partly inferior, or inferior. Styles present. Styles free; base not enlarged, continuous with the achene. Styles 2. Stigmas per style 2–4. Placentation axile. Ovules 25–120. Fruit with calyx persisting (usually), or without calyx persisting; a capsule; spherical, or ellipsoid, or ovoid, or of an unusual shape; 0.3–12 mm long (mean 6 mm); 2–12 mm wide (mean 5 mm); dry; dehiscent; black, or brown, or purple, or green at maturity; hairy (rarely), or glabrous (usually). Legume valves straight. Styles style modified modifying and persisting (usually), or style may persist until dehiscence but is not modified. Seeds 25–50; 0.5–6 mm long (mean 1.3 mm); brown; smooth, or verrucose, or ridged, or winged.
Distribution. Circumpolar (commonly), or amphi-Atlantic, or amphi-Beringian, or North American. Arctic, or low arctic, or alpine. Range in the Canadian Arctic Archipelago wide-spread. Common, or rare, or uncommon. Northern hemisphere: Canada.
Ecology and habitat. Substrate acidic (rarely), or calcareous (commonly), or nitrophilous; moist areas, or rocky sites, or clay.
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.
Miscellaneous. Species in world 580, genera in world 30. Genera in study region: Chrysosplenium, Parnassia, Saxifraga.
Classification. Subclass Dicotyledonae. Dahlgren’s Superorder Rosiflorae, Order Saxifragales. Cronquist’s Subclass Dilleniidae, Order Dilleniales. Takhtajan’s Subclass Rosidae, Superorder Rosanae, Order Saxifragales.
Cite this publication as: ‘C.L. McJannet, S.G. Aiken, M.J. Dallwitz, L.J. Gillespie and L.L. Consaul. 1997 onwards. Saxifragaceae of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 28th November 2000. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), Aiken, Dallwitz et al. (1999), and Aiken, Dallwitz, McJannet, Gillespie, and Consaul (1998) should also be cited (see References).