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12. Sterculiaceae

梧桐科 wu tong ke

Authors: Ya Tang, Michael G. Gilbert & Laurence J. Dorr

Trees or shrubs, rarely herbs or liana; young growth usually stellately hairy; bark mucilaginous and rich in fibers. Leaves alternate; stipules usually present caducous; leaf blade simple, rarely palmately compound, entire, serrate, or parted. Inflorescence axillary or rarely terminal, paniculate, corymbose, racemose, or cymose, rarely solitary. Flowers unisexual, bisexual or polygamous. Sepals (3-)5, ± connate, rarely free, valvate. Petals 5 or lacking, free or adnate to base of androecium, convolutely imbricate. Androgynophore usually present; filaments usually connate into a single tube; staminodes 5, tonguelike or filiform, opposite to sepals, sometimes lacking; anthers 2-celled, longitudinally dehiscent. Pistil consisting of 2-5(or 10-12) ± connate carpels, or a single carpel; ovary superior, 2-5(or 10-12)-loculed; ovules 2 or more per locule; style 1 or as many as carpels. Fruit usually a capsule or follicle, dehiscent or indehiscent, very rarely a berry or nut. Seeds with abundant endosperm or endosperm lacking; embryo straight or curved.

About 68 genera and ca. 1100 species: tropics and subtropics of both hemispheres, a few in temperate regions; 19 genera (two introduced) and 90 species (39 endemic, three introduced) in China.

The Chinese genera fit into four distinct clades which can be treated as subfamilies of an enlarged Malvaceae or as distinct families. These are Sterculioideae/Sterculiaceae s.s. (genera 1-4), Helicteroideae/Helicteraceae (genera 5 and 6), Byttnerioideae/Byttneriaceae (genera 7-13), and Dombeyoideae/Pentapetaceae (genera 14-19).

The record of Hildegardia Schott & Endlicher in China (Bayer & Kubitzki, Fam. Gen. Vasc. Pl. 5: 265. 2003) was based on H. major (W. W. Smith) Kostermans, which is here included within Firmiana.

Hsue Hsiang-hao. 1984. Sterculiaceae. In: Feng Kuo-mei, ed., Fl. Reipubl. Popularis Sin. 49(2): 112-189.

1 Flowers without petals, unisexual or polygamous; fruit apocarpous with separate follicles (Sterculioideae)   (2)
+ Flowers with petals, bisexual; fruit usually syncarpous, sometimes dividing into separate mericarps   (5)
2 (1) Follicles not dehiscent, with wing or prominent keel, 1-seeded; leaf blade abaxially with dense silver-white or yellow-brown scales.   4 Heritiera
+ Follicles dehiscent, without wing or keel, 1- or more seeded; leaf blade abaxially without scales   (3)
3 (2) Seeds long-winged; fruit woody.   1 Pterygota
+ Seeds not winged; fruit leathery or membranous, rarely woody   (4)
4 (3) Fruit leathery, rarely woody, dehiscent when mature.   2 Sterculia
+ Fruit membranous, dehiscent before maturity and foliaceous.   3 Firmiana
5 (1) Ovary on long androgynophore, at least 2 × as long as ovary, often longer than calyx and petals   (6)
+ Ovary sessile or with very short androgynophore (Pterospermum)   (8)
6 (5) Capsule membranous, inflated; seeds 1(or 2) in each cell (Byttnerioideae).   7 Kleinhovia
+ Capsule more or less woody, never membranous, not inflated; seeds 2 or more in each cell (Helicteroideae)   (7)
7 (6) Trees or large shrubs, 6-25 m tall; seeds 1 or 2 per locule, with obvious membranous wing, more than 20 mm; inflorescences terminal; anthers sessile on filament tube or nearly so.   5 Reevesia
+ Shrubs or subshrubs, 0.45-2 m tall; seeds many per locule, without wing, less than 4 mm; inflorescences axillary; anthers with distinct free filaments.   6 Helicteres
8 (5) Flowers without staminodes   (9)
+ Flowers with staminodes   (11)
9 (8) Trees or shrubs; calyx 10-30 mm; stamens 40-50; capsule 3-5 cm, woody or thickly leathery (Dombeyoideae)   14 Eriolaena
+ Herbs or subshrubs; calyx 2-4 mm; stamens 5; capsule 0.3-0.6 cm, membranous (Byttnerioideae)   (10)
10 (9) Capsule 5-celled; styles 5, free or connate at the base only; stigma slightly thickened.   8 Melochia
+ Capsule 1-celled; style 1; stigma fimbriate.   9 Waltheria
11 (8) Flowers cauliflorous, in fascicles on trunk or bases of main branches; fruit fleshy, not dehiscent; seeds without wing (Byttnerioideae).   10 Theobroma
+ Flowers on branchlets; fruit a capsule, dehiscent; seeds with or without wing   (12)
12 (11) Stamens 5, solitary   (13)
+ Stamens (10 or)15(or 20), in 5 fascicles of (2 or)3(or 4), alternating with staminodes (mostly Dombeyoideae)   (15)
13 (12) Semi-shrubs or herbs; flowers solitary; petals persistent (Dombeyoideae).   19 Melhania
+ Trees or large woody liana; flowers in cymes; petals not persistent (Byttnerioideae)   (14)
14 (13) Lianas; staminodes obtuse at tip, lower half connate into tube; capsule with robust and rigid spines, loculicidal into 5 valves.   12 Byttneria
+ Trees; staminodes linear-lanceolate, free; capsule densely hispid, septicidal.   13 Commersonia
15 (12) Herbs   (16)
+ Trees or shrubs, rarely woody climbing lianas   (17)
16 (15) Petals red; capsule ovate-globose.   15 Pentapetes
+ Petals yellow; capsule long cylindric.   16 Corchoropsis
17 (15) Seeds with long membranous wing; staminodes filiform.   17 Pterospermum
+ Seeds wingless; staminodes tongue-shaped or broadly spatulate   (18)
18 (17) Capsule without wing; staminodes tongue-shaped, glabrous; ovules 2 per cell.   18 Paradombeya
+ Capsule 5-winged; staminodes broadly spatulate, emarginate and with grooves at tip, hairy; ovules many per cell (Byttnerioideae).   11 Ambroma

  • List of lower taxa


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