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FOC | Family List | FOC Vol. 8 | Saxifragaceae

26. Hydrangea Linnaeus, Sp. Pl. 1: 397. 1753.

绣球属 xiu qiu shu

Wei Zhaofen (Wei Chao-fen); Bruce Bartholomew

Subshrubs, shrubs, or small trees, erect or climbing, deciduous or evergreen. Branchlets, leaves, and inflorescences variously hairy. Leaves opposite, rarely verticillate, exstipulate; leaf blade simple, margin entire, serrate, or rarely pinnately lobed. Inflorescence terminal, occasionally axillary, a corymbose cyme, umbellate cyme, or thyrse; bracts deciduous. Flowers fertile or sterile. Sterile flowers few (more numerous in cultivated varieties), sometimes absent, borne at margin of inflorescence, with sepals 2 or 5, petaloid, and enlarged. Fertile flowers usually very numerous, bisexual, small; pedicel short. Calyx tube adnate to ovary, 4- or 5-dentate, persistent. Corolla lobes 4 or 5, free, rarely connate and forming a calyptra, ovate or spatulate, valvate. Stamens (8 or)10(or 25), inserted on disc; filaments linear; anthers oblong to subglobose, apex subrounded to obtuse. Ovary inferior to 2/3 superior, imperfectly or perfectly 2-4(or 5)-loculed; placentation parietal or axile; ovules numerous. Styles 2-4(or 5), free or basally connate, persistent; stigmas terminal or decurrent along style adaxially. Fruit a capsule, dehiscing apically among styles, hemispheric to turbinate, small, apex projected or truncate. Seeds numerous, small, winged or wingless; seed coat thin, with reticulate or striate veins.

About 73 species: mainly in E Asia, a few species in SE Asia and the New World; 33 species (25 endemic) in China.

The Japanese species Hydrangea macrophylla (Thunberg) Seringe is cultivated as an ornamental. Records of H. macrophylla var. macrophylla from China (e.g., in FRPS) are probably all from cultivated plants. One of the present authors (Bartholomew) believes that records of H. macrophylla var. normalis E. H. Wilson from China (e.g., in FRPS) are probably referable to related taxa such as H. caudatifolia, H. chungii, or H. stylosa. However, Wei believes that wild-growing H. macrophylla occurs in Guangdong, Guizhou, and Sichuan, with var. normalis in Zhejiang.

One of the present authors (Bartholomew) feels that the three species complexes in Hydrangea would be better treated as the widespread, variable species H. chinensis (to include H. davidii, H. linkweiensis, and H. mangshanensis), H. heteromalla (to include H. bretschneideri, H. dumicola, H. hypoglauca, H. macrocarpa, H. sungpanensis, and H. xanthoneura), and H. aspera (to include H. coacta, H. kawakamii, H. longipes var. fulvescens, and H. longipes var. lanceolata). Bartholomew believes that, with the recognition of these three species in the broader sense, as well as a number of other reductions (H. coenobialis to include H. candida and H. gracilis, H. chungii to include H. caudatifolia, and H. robusta to include H. longipes var. longipes), there are probably about 18 recognizable species of Hydrangea (nine endemic) in China; Wu Zhengyi (editor's note) agrees.

1 Ovary completely inferior; capsule apex truncate.   (2)
+ Ovary 1/3-2/3 superior; capsule apex projected up calyx tube.   (11)
2 (1) Petals apically connate and forming a calyptra; seed wing encircling seed   33 H. anomala
+ Petals free; seeds winged at both ends.   (3)
3 (2) Leaf blade margin entire; bracts closely enveloping inflorescence in bud, ovate-orbicular; vines climbing   32 H. integrifolia
+ Leaf blade margin serrate; bracts not enveloping inflorescence in bud, lanceolate; shrubs or small trees.   (4)
4 (3) Branchlets with branched hairs.   (5)
+ Branchlets glabrous or with simple hairs.   (6)
5 (4) Branchlets, petiole, and peduncle with translucent hairs; leaf blade ovate, oblong-ovate, or elliptic, submembranous or thinly papery   30 H. sargentiana
+ Branchlets, petiole, and peduncle without translucent hairs; leaf blade lanceolate, papery or subleathery   31 H. longifolia
6 (4) Seeds with transverse veins between striate veins   29 H. kawakamii
+ Seeds without transverse veins.   (7)
7 (6) Branchlets 4-angled; petiole long and thick   28 H. robusta
+ Branchlets terete or obscurely 4-angled; petiole usually long and thin or short and thick.   (8)
8 (7) Fertile flowers white; petiole long and thin, leaf blade membranous to thinly papery   26 H. longipes
+ Fertile flowers rose, purple-red, or purple-blue; petiole short and thick; leaf blade papery or thickly so.   (9)
9 (8) Leaf blade abaxially strigose   25 H. strigosa
+ Leaf blade abaxially densely felty tomentose and hirsute, or densely pubescent or villous.   (10)
10 (9) Leaf blade abaxially densely felty tomentose and hirsute   27 H. coacta
+ Leaf blade abaxially densely pubescent or villous   24 H. aspera
11 (1) Projected apical part of capsule conical; free part of petal base truncate; seeds longitudinally striate veined, long winged at both ends; stamens unequal, longer ones inflexed in bud.   (12)
+ Projected apical part of capsule not conical; free part of petal base clawed; seeds net veined, wingless or sometimes very shortly winged; stamens subequal, longer ones not inflexed in bud.   (19)
12 (11) Cymes thyrsoid; leaves opposite or 3-verticillate   16 H. paniculata
+ Cymes corymbose; leaves opposite.   (13)
13 (12) Leaf blade abaxially densely tomentose or velutinous.   (14)
+ Leaf blade abaxially glabrous, subglabrous, pubescent, villous, or acerose hairy.   (15)
14 (13) Leaf blade abaxially densely velutinous; capsule 2.5-3.5 mm in diam.   17 H. heteromalla
+ Leaf blade abaxially densely tomentose; capsule 3-4 mm in diam.   23 H. macrocarpa
15 (13) Leaf blade abaxially glandular granular or glandular papillate.   (16)
+ Leaf blade eglandular on both surfaces.   (17)
16 (15) Leaf blade abaxially glandular granular; styles subulate or not in fruit   18 H. hypoglauca
+ Leaf blade abaxially glandular papillate; styles clavate in fruit   19 H. sungpanensis
17 (15) Anthers purple-blue   22 H. dumicola
+ Anthers yellow.   (18)
18 (17) First and 2nd year's branchlets without lenticels; leaf blade abaxially gray-white villous or glabrescent   20 H. bretschneideri
+ Second and sometimes 1st year's branchlets with conspicuous lenticels; leaf blade abaxially glabrous except grayish pubescent to densely slightly crisped villous along veins   21 H. xanthoneura
19 (11) Ovary less than 1/2 superior; seeds wingless or sometimes very shortly winged at one or both ends.   (20)
+ Ovary at least 1/2 superior; seeds wingless.   (24)
20 (19) Leaf blade lanceolate, margin slightly reflexed, entire or sparsely serrulate distally; inflorescence branches unequal   11 H. kwangsiensis
+ Leaf blade elliptic to broadly so or obovate to obovate-orbicular, margin not reflexed, serrate or roughly long dentate; inflorescence branches subequal.   (21)
21 (20) Leaf blade densely roughly villous or pubescent on both surfaces, hairs erect, spread along veins.   (22)
+ Leaf blade glabrous on both surfaces or sparsely crisped pubescent along veins.   (23)
22 (21) Leaf blade densely roughly villous on both surfaces especially abaxially; capsule 2.5-3 mm in diam.   12 H. chungii
+ Leaf blade pubescent on both surfaces; capsule 1.5-2 mm in diam.   13 H. caudatifolia
23 (21) Capsule oblong-ovoid; styles short and thick, ca. 1 mm in fruit; anthers yellow   14 H. zhewanensis
+ Capsule subglobose; styles slender, 2.5-3 mm in fruit; anthers blue   15 H. stylosa
24 (19) Inflorescence with sterile flowers.   (25)
+ Inflorescence without sterile flowers.   (29)
25 (24) Second year's or older branchlets gray-white, bark not peeled off.   (26)
+ Second year's or older branchlets purplish, red-brown, or brown, bark peeled off into irregular fragments.   (27)
26 (25) Leaf blade elliptic to suboblong, membranous, adaxially sparsely villous and pubescent; lowest inflorescence branch subtended by a leaf; petals elliptic-rhomboid, 2-2.5 × ca. 1 mm   4 H. mangshanensis
+ Leaf blade linear-lanceolate to lanceolate, papery, adaxially glossy and glabrous; lowest inflorescence branch not subtended by a leaf; petals elliptic to narrowly so, 3-4 × 1-1.5 mm   5 H. stenophylla
27 (25) Inflorescence with a 3-5 cm peduncle, branches 3, central branch usually shorter and thinner   3 H. linkweiensis
+ Inflorescence without a peduncle, branches 3 or 5, equal or central one longer and thicker.   (28)
28 (27) Styles erect or slightly spreading in fruit; inflorescences umbellate or subcorymbose; petals yellow   1 H. chinensis
+ Styles curved outward in fruit; inflorescences corymbose; petals deep blue   2 H. davidii
29 (24) Leaf blade dark purple-red to dark brown and glossy on both surfaces when dry, or abaxially pearly gray and adaxially yellowish, both surfaces glabrous or abaxially sparsely appressed pubescent along midvein and secondary veins.   (30)
+ Leaf blade neither dark purple-red on both surfaces when dry nor abaxially pearly gray, one or both surfaces densely villous, sparsely pubescent, or puberulous.   (31)
30 (29) Leaf blade usually dark purple-red to dark brown and glossy on both surfaces when dry, narrowly elliptic to lanceolate, papery, both surfaces glabrous; stigmas not curved outward, not or slightly decurrent along style adaxially   6 H. lingii
+ Leaf blade abaxially pearly gray and adaxially yellowish when dry, elliptic to oblong, membranous, both surfaces glabrous or abaxially sparsely appressed pubescent along midvein and secondary veins; stigmas curved outward, decurrent along style adaxially   7 H. candida
31 (29) Leaf blade densely villous   10 H. kwangtungensis
+ Leaf blade sparsely pubescent or puberulous.   (32)
32 (31) Leaf blade 3-8.5 × 1-3 cm, membranous or thinly papery, both surfaces sparsely pubescent or abaxially subglabrous; branchlets slender; inflorescence 2-6 cm wide, branches slender   8 H. gracilis
+ Leaf blade 9-20 × 2.5-5 cm, papery to thickly so, abaxially sparsely puberulent except along veins; branchlets thick; inflorescence 7-12 cm wide, branches thick   9 H. coenobialis

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