Family Saxifragaceae
Saxifragaceae Juss.Including Bicornaceae DulacExcluding Eremosynaceae, Escalloniaceae, Francoaceae, Grossulariaceae, Lepuropetalaceae, Parnassiaceae, Penthoraceae, Vahliaceae Habit and leaf form. Herbs; non-laticiferous and without coloured juice. Plants succulent (somewhat, sometimes), or non-succulent. Annual, or perennial; with a basal aggregation of leaves, or with neither basal nor terminal aggregations of leaves. Mesophytic, or xerophytic (many arctic/alpine). Leaves small, or medium-sized; alternate (nearly always), or opposite (sometimes); usually spiral; ‘herbaceous’, or fleshy (occasionally); petiolate to sessile; sheathing, or non-sheathing. Leaf sheaths not tubular; with free margins. Leaves not gland-dotted; simple. Lamina dissected, or entire; when incised, pinnatifid; one-veined, or pinnately veined, or palmately veined; cross-venulate. Leaves exstipulate. Lamina margins entire, or crenate, or serrate, or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hydathodes commonly present. Stomata present; usually anomocytic. Lamina dorsiventral, or isobilateral, or centric. Minor leaf veins without phloem transfer cells (Chrysosplenium, Saxifraga, Tiarella). Stem anatomy. Nodes tri-lacunar (usually), or multilacunar (e.g. Astilbe). Cortical bundles present, or absent. Medullary bundles present, or absent. Secondary thickening absent, or developing from a conventional cambial ring (?). Vessel end-walls simple. Sieve-tube plastids S-type. Reproductive type, pollination. Plants hermaphrodite. Floral nectaries usually present. Nectar secretion from the disk. Pollination entomophilous. Inflorescence, floral, fruit and seed morphology. Flowers solitary (rarely), or aggregated in ‘inflorescences’; in cymes, or in racemes, or in spikes, or in heads, or in fascicles, or in panicles. The ultimate inflorescence unit cymose, or racemose. Inflorescences scapiflorous, or not scapiflorous; various. Flowers small, or medium-sized; regular, or somewhat irregular to very irregular. The floral irregularity when irregular, involving the perianth (the petals dimorphous). Flowers 5 merous; cyclic; pentacyclic (usually), or tetracyclic. Floral receptacle (when flower hypogynous) markedly hollowed to not markedly hollowed. Free hypanthium present, or absent. Hypogynous disk present (usually), or absent; intrastaminal. Perianth with distinct calyx and corolla (usually), or sepaline (corolla sometimes lacking); usually 10; usually 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous; regular; imbricate, or valvate; with the median member posterior. Corolla 5; 1 whorled; polypetalous, or gamopetalous; imbricate, or valvate; regular; white, or yellow, or red, or pink (not blue). Petals clawed (often), or sessile. Androecium 10 (usually), or 5. Androecial members free of the perianth; all equal, or markedly unequal; free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens 10 (usually), or 5; diplostemonous (usually), or isomerous with the perianth; usually alternisepalous (obdiplostemonous). Anthers cohering (in pairs), or separate from one another; basifixed (mostly), or dorsifixed (slightly only, e.g. Heuchera, Bergenia); versatile; dehiscing via longitudinal slits; slightly introrse, or latrorse (e.g. Saxifraga), or extrorse and introrse (Tolmiea, with the median extrorse and the laterals introrse); tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer, or initially with more than one middle layer (1 or 2). Tapetum glandular. Pollen grains aperturate; 3(–5) aperturate; colporate (or colporoidate); 2-celled (in Astilbe, Bergenia, Heuchera and Saxifraga). Gynoecium 2(–5) carpelled. Carpels reduced in number relative to the perianth (usually), or isomerous with the perianth (when carpels more or less free). The pistil 2(–3) celled. Gynoecium apocarpous to syncarpous; semicarpous to synovarious (i.e. carpels more or less joined below); superior to inferior. Ovary 2(–3) locular. Gynoecium when G2 (i.e. usually), median. Styles 2(–3); free; apical; shorter than the ovary. Stigmas dorsal to the carpels; wet type, or dry type; papillate; Group II type, or Group III type. Placentation axile. Ovules 9–30 per locule (in several rows); pendulous, or ascending; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; proliferating (rarely, to 5 cells), or not proliferating; ephemeral, or persistent. Synergids hooked (and usually with filiform apparatus). Endosperm formation cellular, or helobial. Embryogeny solanad. Fruit non-fleshy; an aggregate (rarely), or not an aggregate; dehiscent; a capsule. Capsules usually septicidal. Fruit 20–50 seeded (‘very numerous’). Seeds endospermic. Endosperm oily. Seeds minute to small. Cotyledons 2. Embryo achlorophyllous (3/4); straight. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar. Physiology, biochemistry. Cyanogenic, or not cyanogenic. Iridoids not detected. Proanthocyanidins present, or absent; when present, cyanidin, or cyanidin and delphinidin. Flavonols present; quercetin, or kaempferol and quercetin, or kaempferol, quercetin, and myricetin. Ellagic acid present (Bergenia), or absent (4 species, 4 genera). Arbutin present, or absent (?). Aluminium accumulation demonstrated, or not found (usually?). C3 and CAM (?). C3 physiology recorded directly in Heuchera. Anatomy non-C4 type (Heuchera). Geography, cytology. Frigid zone to temperate. Chiefly North temperate, a few Southern temperate and tropical mountains. Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Saxifragales. Cronquist’s Subclass Rosidae; Rosales. APG 3 core angiosperms; core eudicot; unplaced at Superordinal level; Order Saxifragales. Species 580. Genera about 30; Astilbe, Astilboides, Bensoniella, Bergenia, Bolandra, Boykinia, Chrysosplenium, Conimitella, Darmera (Peltiphyllum), Elmera, Heuchera, Jepsonia, Leptarrhena, Lithophragma, Mitella, Mukdenia, Oresitrophe, Rodgersia, Saxifraga, Saxifragella, Saxifragodes, Saxifragopsis, Suksdorfia, Sullivantia, Tanakaea, Tellima, Tiarella, Tolmiea. Illustrations. |
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