Herbs, perennial, rarely biennial (Saxifraga) or annual (Cascadia, Saxifraga), rhizomatous or not, stoloniferous or not, persistent stem ± erect as caudex, horizontal as rhizome, or intergrading, branched or unbranched, sometimes bearing bulbils (Bolandra, Lithophragma, Micranthes, Saxifraga, Suksdorfia). Flowering stems appearing in spring, summer, or autumn with leaves usually present (usually appearing in autumn or winter after basal leaves have withered in Jepsonia), leafless, or leafy and bearing 1-5 cauline leaves proximally, glabrous or short to long stipitate-glandular or eglandular, hairs usually multicellular (unicellular in Astilbe, Saxifragopsis). Leaves usually in basal rosettes, sometimes cauline, usually alternate, sometimes opposite (Chrysosplenium, Lithophragma, Mitella, Saxifraga), usually simple (compound in Astilbe, sometimes compound in Lithophragma, Tiarella); stipules absent or present; petiole absent or present, usually not jointed distally at attachment to blade (jointed distally in Saxifragopsis), usually not peltate (peltate in Darmera), not producing adventitious buds at apices of petioles of basal rosette and cauline leaves (usually producing adventitious buds at apices of petioles in Tolmiea); blade margins entire, crenate, serrate, or dentate, ciliate or glandular-ciliate. Inflorescences usually terminal racemes, panicles, cymes (simple or compound), thyrses (with lateral dichasial or monochasial cymose branches), or solitary flowers (Chrysosplenium, Lithophragma), sometimes axillary cymes (Chrysosplenium), usually arising from terminal or axillary buds in rosettes, 2-300(-1000+)-flowered, bracteate or ebracteate. Flowers usually bisexual, sometimes unisexual (Astilbe, Saxifraga), homostylous (heterostylous in Jepsonia), usually radially symmetric, sometimes bilaterally symmetric (Bensoniella, Heuchera, Micranthes, [Saxifraga], Tiarella, Tolmiea); perianth and androecium hypogynous, perigynous, or epigynous; hypanthium free (Bolandra, Jepsonia) or ± adnate to ovary, usually not split to base (split to base in Tolmiea); sepals usually (4-)5(-6), distinct; petals usually (4-)5(-6) or absent, distinct, lobed or unlobed; nectary disc often encircling ovary distally at junction of ovary and free portion of hypanthium; stamens (2-)5(-9)10; anthers usually dehiscent longitudinally, rarely by broad terminal openings (Leptarrhena); staminodes absent; pistils 1, sometimes appearing 2-3+ (Micranthes), usually 2-carpellate, rarely 3-carpellate (Astilbe, Lithophragma, Micranthes), carpels connate for full length of ovary to barely connate proximally, equal, rarely unequal (Tiarella); ovary superior to inferior, 1-2(-3)-locular, ovaries fully connate when 1-locular, proximally connate to varying degrees when 2- and 3-locular (Astilbe, Micranthes); placentation axile, appearing marginal when ovaries are barely connate, or parietal; ovules anatropous, usually bitegmic, rarely unitegmic (most Micranthes), crassinucellate; styles 2-3(-4), distinct or connate (Saxifragopsis); stigmas 2-3(-4), capitate. Fruits capsular, sometimes folliclelike (Cascadia, Micranthes), 2-3(-4)-beaked, equally valvate (unequally valvate in Tiarella), dehiscence septicidal between beaks. Seeds 5-200, tan, brown, dark brown, black, yellowish brown, reddish brown, or red, rarely winged (Astilbe, Jepsonia, Sullivantia), ellipsoid, fusiform, ovoid, oblong, spheroid, oblong-cylindric, flat, or straight on 1 side, convex on other, rarely prismatic, smooth, wrinkled, ribbed, papillate, pitted, or ridged, tuberculate, warty, spiny, cellular-rugulose, or muricate; embryo straight; endosperm oily, copious.
Herbs or shrubs, rarely trees or vines. Leaves simple or compound, usually alternate or opposite, usually exstipulate. Flowers usually in cymes, panicles, or racemes, rarely solitary, usually bisexual, rarely unisexual, hypogynous or ± epigynous, rarely perigynous, usually biperianthial, rarely monochlamydeous, actinomorphic, rarely zygomorphic, 4- or 5(-10)-merous. Sepals sometimes petal-like. Petals usually free, sometimes absent. Stamens (4 or)5-10 or many; filaments free; anthers 2-loculed; staminodes often present. Carpels 2, rarely 3-5(-10), usually ± connate; ovary superior or semi-inferior to inferior, 2- or 3-5(-10)-loculed with axile placentation, or 1-loculed with parietal placentation, rarely with apical placentation; ovules usually many, 2- to many seriate, crassinucellate or tenuinucellate, sometimes with transitional forms; integument 1- or 2-seriate; styles free or ± connate. Fruit a capsule or berry, rarely a follicle or drupe. Seeds albuminous, rarely not so; albumen of cellular type, rarely of nuclear type; embryo small.
Seeds usually numerous, small, with endosperm; embryo minute, straight
Ovary 1–5-celled, free or adnate to the receptacle; styles usually free; ovules numerous, on axile or parietal placentas or the latter pendulous from the apex of the cells
Stamens inserted with the petals, 5–10; filaments free; anthers 2-celled, dehiscing longitudinally
Petals alternate with the sepals or absent, often clawed, perigynous or rarely epigynous
Sepals usually 5, imbricate or valvate
Flowers actinomorphic, hermaphrodite, rarely solitary
Leaves usually alternate (opposite in Vahlia), exstipulate
SELECTED REFERENCES Gornall, R. J. and B. A. Bohm. 1980. The use of flavonoids in the taxonomy of Boykinia and allies (Saxifragaceae). Canad. J. Bot. 58: 1768-1779. Gornall, R. J. and B. A. Bohm. 1984. Breeding systems and relationships among species of Boykinia and related genera (Saxifragaceae). Canad. J. Bot. 62: 33-37. Gornall, R. J. and B. A. Bohm. 1985. A monograph of Boykinia, Peltoboykinia, Bolandra and Suksdorfia (Saxifragaceae). Bot. J. Linn. Soc. 90: 1-71. Johnson, L. A. and D. E. Soltis. 1994. matK DNA sequences and phylogenetic reconstruction in Saxifragaceae, s.s. Syst. Bot. 19: 143-156. Morgan, D. R. and D. E. Soltis. 1993. Phylogenetic relationships among members of Saxifragaceae sensu lato based on rbcL sequence data. Ann. Missouri Bot. Gard. 80: 631-660. Savile, D. B. O. 1975. Evolution and biogeography of Saxifragaceae with guidance from their rust parasites. Ann. Missouri Bot. Gard. 62: 354-361. Small, J. K. and P. A. Rydberg. 1905b. Saxifragaceae. In: N. L. Britton et al., eds. 1905+. North American Flora.... 47+ vols. New York. Vol. 22, pp. 81-158. Soltis, D. E. 1980. Karyotypic relationships among species of Boykinia, Heuchera, Mitella, Sullivantia, Tiarella, and Tolmiea (Saxifragaceae). Syst. Bot. 5: 17-29. Soltis, D. E. 1984e. Karyotypic relationships among Elmera, Heuchera, and Tellima (Saxifragaceae). Syst. Bot. 9: 6-11. Soltis, D. E. 1988. Karyotypes of Bensoniella, Conimitella, Lithophragma, and Mitella and relationships in Saxifraginae (Saxifragaceae). Syst. Bot. 13: 64-72. Soltis, D. E. 2007. Saxifragaceae. In: K. Kubitzki et al., eds. 1990+. The Families and Genera of Vascular Plants. 9+ vols. Berlin etc. Vol. 9, pp. 418-435. Soltis, D. E. et al. 1990b. rbcL sequence divergence and phylogenetic relationships of Saxifragaceae sensu lato. Proc. Natl. Acad. Sci. U.S.A. 87: 4640-4644. Soltis, D. E. et al. 1993. Molecular systematics of Saxifragaceae sensu stricto. Ann. Missouri Bot. Gard. 80: 631-660. Soltis, D. E. et al. 2001. Elucidating deep-level phylogenetic relationships in Saxifragaceae using sequences for six chloroplastic and nuclear DNA regions. Ann. Missouri Bot. Gard. 88: 669-693. Soltis, D. E. and B. A. Bohm. 1985. Chromosomal and flavonoid chemical confirmation of intergeneric hybridization between Tolmiea and Tellima (Saxifragaceae). Canad. J. Bot. 63: 1309-1312. Soltis, D. E. and P. S. Soltis. 1997. Phylogenetic relationships in Saxifragaceae sensu lato: A comparison of topologies based on 18s rDNA and rbcL sequences. Amer. J. Bot. 84: 504-522. Soltis, D. E., P. S. Soltis, T. G. Collier, and M. L. Edgerton. 1991. Chloroplast DNA variation within and among genera of the Heuchera group (Saxifragaceae): Evidence for chloroplast transfer and paraphyly. Amer. J. Bot. 78: 1091-1112. Spongberg, S. A. 1972. The genera of Saxifragaceae in the southeastern United States. J. Arnold Arbor. 53: 409-498.