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Saxifragaceae A. L. Jussieu

虎耳草科 hu er cao ke

Authors: Jin-tang Pan, Cuizhi Gu, Shumei Huang, Chao-fen Wei, Shu-ying Jin, Lingdi Lu, Shinobu Akiyama, Crinan Alexander, Bruce Bartholomew, James Cullen, Richard J. Gornall, Ulla-Maj Hultgård, Hideaki Ohba & Douglas E. Soltis

Rodgersia pinnata

Credit: Harvard University Herbaria

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.

About 80 genera and 1200 species: worldwide; 29 genera (two endemic), and 545 species (354 endemic, seven introduced) in China.

During the past several years, cladistic analyses of morphological, chemical, and DNA data have made it clear that the recognition of the Saxifragaceae sensu lato (Engler, Nat. Pflanzenfam. 18a: 74-226. 1928) is untenable. Among the angiosperm families, Saxifragaceae sensu lato may in fact represent the most extreme example of a polyphyletic assemblage. For example, recent analyses of DNA sequence data indicate that these taxa represent at least ten separate evolutionary lines, many of which are only distantly related to one another (Morgan & Soltis, Ann. Missouri Bot. Gard. 80: 631-660. 1993; Soltis & Soltis, Amer. J. Bot. 84: 504-522. 1997). Furthermore, very large molecular phylogenetic analyses of hundreds of angiosperms indicate that these separate lineages are distributed among four of the six traditionally recognized subclasses of dicotyledons (Savolainen et al., Syst. Biol. 49: 306-362. 2000; Soltis et al., Nature 402: 402-404. 1999). These recent studies have also greatly clarified how this phylogenetically diverse assemblage should be divided into families and treated taxonomically (see The Angiosperm Phylogeny Group (APG), Ann. Missouri Bot. Gard. 85: 531-553. 1998). Recent studies of DNA sequence data have clarified both the circumscription and affinities of a narrowly defined Saxifragaceae (Saxifragaceae sensu stricto) and Hydrangeaceae (Soltis et al., Amer. J. Bot. 82: 504-514. 1995; Savolainen et al., loc. cit.; Soltis et al., loc. cit. 1999). Saxifragaceae sensu stricto should consist only of Saxifragoideae, a group of about 30 herbaceous genera. Members of Saxifragaceae sensu stricto from the Chinese flora include Astilbe, Astilboides, Bergenia, Chrysosplenium, Mitella, Mukdenia, Oresitrophe, Rodgersia, Saxifraga, Tanakaea, Tiarella, and the recently described Saniculiphyllum. Close relatives of Saxifragaceae sensu stricto include Itea, Penthorum, and Ribes. These genera, the sole members of Iteoideae, Penthoroideae, and Ribesioideae, respectively, are also best treated in separate families: Iteaceae, Penthoraceae, and Grossulariaceae (see APG, loc. cit.). These taxa, as well as several others, such as Crassulaceae, are basal to a large assemblage of taxa, most of which were traditionally placed in Rosidae. Sequence data also indicate that Parnassia (the sole member of the Parnassioideae) is a more derived member of the rosid alliance, most closely related to Brexia and Lepuropetalon (also part of Saxifragaceae sensu lato) and Celastraceae. Parnassia and Lepuropetalon should be placed in Parnassiaceae with Brexia part of an expanded Celastraceae (APG, loc. cit.).

Both morphological and molecular data indicate that Hydrangeoideae and Escallonioideae are, in contrast, allied with taxa traditionally placed in Asteridae. Hydrangeoideae are a well-defined, monophyletic lineage that should be treated as Hydrangeaceae. In China they include Cardiandra, Decumaria, Deinanthe, Deutzia, Dichroa, Hydrangea, Kirengeshoma, Philadelphus, Pileostegia, Platycrater, and Schizophragma, and are closely allied with families such as Cornaceae, Loasaceae, and Nyssaceae. Escallonioideae appear to be polyphyletic, and this group of approximately 14 genera is in need of thorough study. Members of this subfamily are allied with several different lineages of higher asterids. Polyosma, the only member of Escallonioideae in China, appears closely allied with Caprifoliaceae (Xiang & Soltis in Boufford & Ohba, Sino-Japanese Flora: its Characteristics and Diversification, 1998).

Nevertheless, in the present account, the Saxifragaceae are retained in the sense of FRPS, using the same sequence of genera and indicating the subfamilies in the key below, in order to facilitate comparison with that flora.

The genus Changiodendron R. H. Miao (Acta Sci. Nat. Univ. Sunyatseni 34: 65. 1995) and its single species, C. guangxiense R. H. Miao (loc. cit.: 66), was described from Guangxi (Napo Xian) and stated to belong to the Iteaceae (i.e., Iteoideae). However, Peng (Acta Bot. Yunnan. 18: 299-300. 1996) demonstrated that C. guangxiense is a synonym of Sabia parviflora Wallich (Sabiaceae).

Pan Jin-tang. 1992. Saxifragaceae (1) [Penthoroideae, Saxifragoideae]. In: Pan Jin-tang, ed., Fl. Reipubl. Popularis Sin. 34(2): 1-309; Hwang Shu-mei, Wei Chao-fen, Lu Ling-ti, Ku Tsue-chih & Jin Shu-ying. 1995. Saxifragaceae (2) [Parnassioideae, Hydrangeoideae, Escallonioideae, Iteoideae, Ribesioideae]. In: Lu Ling-ti & Hwang Shu-mei, eds., Fl. Reipubl. Popularis Sin. 35(1): 1-406.

1 Plants woody or herbs; leaves opposite or alternate, rarely subverticillate or cespitose.   (2)
+ Plants herbs; leaves usually alternate.   (16)
2 (1) Stamens as many as sepals; leaves usually alternate, opposite or subopposite in Polyosma.   (3)
+ Stamens ca. 2 × as many as sepals, sometimes more; leaves usually opposite or verticillate, alternate or fascicled in Cardiandra (Hydrangeoideae).   (5)
3 (2) Leaves opposite or subopposite; fruit a 1-seeded berry (Escallonioideae)   27 Polyosma
+ Leaves alternate; fruit a capsule or many-seeded berry.   (4)
4 (3) Leaves never lobed; stipules present, linear; sepals not petal-like; petals narrow; ovary 2-loculed; fruit a capsule (Iteoideae)   28 Itea
+ Leaves often palmately lobed; stipules absent, spines or prickles sometimes present; sepals usually petal-like; petals usually scalelike; ovary 1-loculed; fruit a berry (Ribesioideae)   29 Ribes
5 (2) Herbs; leaf blade palmately lobed; stamens 3 × as many as petals   16 Kirengeshoma
+ Shrubs, scandent shrubs, or herbs; leaf blade not palmately lobed; stamens numerous or 2 × as many as petals.   (6)
6 (5) Filaments subulate, flat, apex 2-dentate or 2-lobed; shrubs; calyx lobes never enlarged and petaloid.   (7)
+ Filaments linear, neither subulate nor flat; herbs or shrubs; calyx lobes sometimes enlarged and petaloid.   (8)
7 (6) Leaves often stellate hairy; petals 5; stamens 10(-15); capsule 3-5-valved, loculicidally dehiscent   17 Deutzia
+ Leaves not stellate hairy; petals 4; stamens 20-40; capsule 4-valved, loculicidally or septicidally dehiscent   18 Philadelphus
8 (6) Inflorescences with all flowers fertile; calyx lobes never petaloid.   (9)
+ Inflorescences with both fertile and sterile flowers (except Schizophragma crassum); calyx lobes ± petaloid.   (12)
9 (8) Styles 2-6.   (10)
+ Style 1.   (11)
10 (9) Fruit a fleshy berry   21 Dichroa
+ Fruit a capsule   26 Hydrangea
11 (9) Sepals and petals 7-10, apex free; stamens 20-30; stigma discoid   19 Decumaria
+ Sepals and petals 4 or 5, apex connate and forming a calyptra; stamens 8-10; stigma conical   20 Pileostegia
12 (8) Leaves alternate; anthers obcordate, apex truncate, connective dilated   22 Cardiandra
+ Leaves opposite or verticillate; anthers oblong, ellipsoid, or subglobose, apex obtuse to subrounded, connective not dilated.   (13)
13 (12) Style 1; sterile flowers (if present) with 1(-3 in Schizophragma integrifolium) enlarged calyx lobe   24 Schizophragma
+ Styles 2 or more; sterile flowers (if present) with more than 1 enlarged calyx lobe.   (14)
14 (13) Sterile flowers with connate, enlarged, petaloid calyx lobes   23 Platycrater
+ Sterile flowers with free, enlarged, petaloid calyx lobes, or sterile flowers absent.   (15)
15 (14) Herbs perennial or subshrubs, with horizontal rhizomes; stem simple; petals imbricate in bud; styles 5, connate into a column   25 Deinanthe
+ Shrubs or subshrubs, sometimes scandent, rarely small trees; stems often branched; petals valvate in bud; styles 2-5, free or connate only at base   26 Hydrangea
16 (1) Flower solitary; stamens 5, staminodes 5, conspicuous, spreading into a lamina, usually distally lobed, inserted opposite petals; ovary 1-loculed (Parnassioideae)   15 Parnassia
+ Flowers usually in cymes, racemes, or panicles, sometimes solitary; stamens 4-14, staminodes absent; ovary 1-5-loculed.   (17)
17 (16) Leaves membranous; inflorescence a helicoid cyme; stamens (6-)10; ovary 5-loculed (Penthoroideae)   1 Penthorum
+ Leaves usually not membranous; inflorescence often not helicoid; stamens 4-14; ovary usually less than 5-loculed, rarely more (Saxifragoideae).   (18)
18 (17) Leaves usually compound, rarely simple; sepals 4 or 5, sometimes 1-3 or absent; carpels 2 or 3(or 4); ovary 2- or 3(or 4)-loculed with axile placentation or 1-loculed with marginal placentation.   (19)
+ Leaves simple; petals 5(or 6) or absent; carpels 2(-5); ovary 2(-5)-loculed with axile placentation, or 1-loculed with marginal or parietal placentation, sometimes proximally with 2 terminal, parietal placentas and distally with marginal placentation.   (21)
19 (18) Leaves simple, leaf blade peltate, margin palmatilobed; petals 4 or 5; stamens (6-)8; carpels 2(-4), ovary 2(-4)-loculed   2 Astilboides
+ Leaves usually compound (or, if simple, leaf blade not peltate), usually 3-5-lobed; petals 1-5 or absent; stamens (5-)8-10(-14); carpels 2 or 3, ovary 1-3-loculed.   (20)
20 (19) Leaves palmately, pinnately, or subpinnately compound; bract absent; sepals (4 or)5(-7); petals usually absent; stamens 10(-14); ovary 2- or 3-loculed with axile placentation   3 Rodgersia
+ Leaves ternately compound, rarely simple; bracts conspicuous; sepals (4 or)5; petals 1-5, sometimes more or absent; stamens (5-)8-10; ovary 2(or 3)-loculed with axile placentation or 1-loculed with marginal placentation   4 Astilbe
21 (18) Leaves all basal; bracts absent; sepals 5-7 or absent; stamens 5 or 6 or 10-14.   (22)
+ Leaves all basal or both basal and cauline; bracts conspicuous; sepals 4 or 5(-7); petals 5 or absent; stamens 4-10.   (23)
22 (21) Leaf blade ovate to cordate, glandular hairy abaxially, glabrous adaxially, margin irregularly dentate; sepals 5-7, unequal, many veined; petals absent; stamens 10-14   5 Oresitrophe
+ Leaves broadly ovate to orbicular, glabrous on both surfaces, margin palmately 5-7(-9)-cleft, lobes serrate; sepals 5 or 6, subequal, 1-veined; petals 5 or 6(or 7), white; stamens 5 or 6(or 7)   6 Mukdenia
23 (21) Carpels 2 or 3, ovary 2- or 3-loculed   7 Saniculiphyllum
+ Carpels 2, ovary 1- or 2-loculed, or proximally 2-loculed and distally 1-loculed.   (24)
24 (23) Sepals 5; petals 5; stamens 10; ovary 2-loculed with axile placentation or 1-loculed with marginal placentation.   (25)
+ Sepals 4 or 5(-7); petals 5 or absent; stamens 4-10; ovary usually 1-loculed with 2 parietal placentas, or proximally 2-loculed with axile placentation and distally 1-loculed with marginal placentation.   (27)
25 (24) Herbs perennial, rarely annual or biennial; inflorescence a cyme or flower solitary; flowers usually actinomorphic, rarely zygomorphic; receptacle cyathiform or saucer-shaped; fruit a capsule, rarely a follicle   10 Saxifraga
+ Herbs perennial; inflorescence a cyme; flowers actinomorphic; receptacle cyathiform; fruit a capsule.   (26)
26 (25) Leaves all basal, petiole short, broad, sheathing at base, leaf blade not peltate, margin entire or dentate; hypanthium scarcely adnate to ovary; petals white, red, or purple, margin entire; ovary subsuperior, proximally 2-loculed with axile placentation and distally 1-loculed with marginal placentation; seeds angular   8 Bergenia
+ Leaves both basal and cauline, stipules membranous, leaf blade peltate, margin palmatilobed; hypanthium proximally adnate to ovary; petals yellowish, margin usually sparsely denticulate; ovary semi-inferior, 2-loculed with axile placentation; seeds tuberculate   9 Peltoboykinia
27 (24) Stipules conspicuous; sepals 5; petals 5, sometimes absent; stamens 5 or 10.   (28)
+ Stipules absent; sepals 4 or 5(-7); petals absent; stamens 4-10.   (29)
28 (27) Leaves simple or trifoliolate; inflorescence terminal or axillary, racemose or paniculate; petals entire; stamens 10; fruit with 2 distinctly unequal carpels   11 Tiarella
+ Leaves simple; inflorescence terminal, racemose; petals usually pinnatifid, rarely entire; stamens 5 or 10; fruit with 2 subequal carpels   12 Mitella
29 (27) Cauline leaves alternate or opposite; inflorescence usually cymose; sepals 4(or 5); stamens 4-8(-10); ovary subsuperior or semi-inferior to subinferior   14 Chrysosplenium
+ Cauline leaves absent; inflorescence paniculate or racemose; sepals (4 or)5(-7); stamens 8-10; ovary subsuperior   13 Tanakaea

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