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FOC | Family List | FOC Vol. 12 | Sterculiaceae

17. Pterospermum Schreber, Gen. Pl. 2: 461. 1791.

翅子树属 chi zi shu shu

Trees or shrubs, stellate velutinous or scurfy and scaly. Leaves simple; stipules linear to palmately fimbriate, sometimes forming nectaries, caducous; petiole short; leaf blade lobed or not, leathery, base often oblique, margin entire or serrate, apex sometimes truncate; juvenile leaves sometimes much larger, petiole long, leaf blade often with peltate base and prominently palmately lobed. Inflorescence axillary, 1-flowered or cymose and 1-5-flowered. Flowers bisexual; epicalyx lobes usually 3, usually distant from calyx, entire, fimbriate, or palmately lobed, rarely absent, caducous. Calyx 5(or 6)-lobed, divided nearly to base, usually spreading to ± reflexed, caducous. Petals 5, white or yellow, often erect. Androgynophore present, very short, glabrous. Stamens 15, in 5 groups of 3 alternating with staminodes; filaments connate into tube, free at top; anthers 2-celled, cells parallel, connective pointed; staminodes 5, filiform, longer and thicker than filaments. Ovary 5-locular; ovules 4-22 per locule; style clavate or filiform; stigma longitudinally 5-grooved. Fruit a schizocarp, cylindric or ovoid, angular or rounded, usually woody, sometimes leathery, dehiscent into 5 loculicidal mericarps when mature. Seeds 2 to many per locule, with long, oblong, membranous wing; endosperm scanty or absent; cotyledons usually plicate, simple. 2n = 38.

Between 18 and 40 species: tropical and subtropical Asia; nine species (five endemic) in China.

Sterculia peltata G. Don (Gen. Hist. 1: 517. 1831), based on material from China, has long petiolate 5-lobed peltate leaves that are abaxially puberulent and adaxially glabrous, and has stems and petioles with a white tomentum. The leaf form is much more suggestive of juvenile material of Pterospermum than a species of Sterculia but the white indumentum is difficult to match with the species known from China.

Key to flowering material (flowers not known for Pterospermum yunnanense)

1 Leaf blade 24-34 × 14-29 cm; sepals to 9 cm.   1 P. acerifolium
+ Leaf blade 4.5-18 × 1.5-11 cm; sepals 1.5-6.5 cm   (2)
2 (1) Petals obovate, ca. 2.8 cm wide.   3 P. kingtungense
+ Petals linear to oblanceolate, 0.4-1.1 cm wide   (3)
3 (2) Leaf blade of mature trees very variable, usually oblique, lobes very irregular.   2 P. proteus
+ Leaf blade of mature trees uniform, usually bilaterally symmetrical, entire or with apex regularly 3-5-lobed   (4)
4 (3) Leaf blade of mature trees broadest above middle, apex 3-5-lobed.   4 P. truncatolobatum
+ Leaf blade of mature trees oblong, elliptic, or broadest at or below middle, apex not lobed   (5)
5 (4) Epicalyx lobes linear-divided; pedicel 3-5 cm   9 P. lanceifolium
+ Epicalyx lobes entire; pedicel to 1.5 cm   (6)
6 (5) Leaf blade base obtuse or truncate, rarely shallowly obliquely cordate; sepals 2.5-2.8 × ca. 0.4 cm.   8 P. heterophyllum
+ Leaf blade base obliquely cordate or rounded; sepals 3.5-4.5 × 0.25-0.4 cm   (7)
7 (6) Leaf blade base obliquely cordate; sepals ca. 4.5 × 0.4 cm; androgynophore ca. 2 cm.   6 P. niveum
+ Leaf blade base obliquely rounded; sepals ca. 3.5 × 0.25 cm; androgynophore ca. 0.8 cm.   7 P. menglunense

List of Keys

Lower Taxa


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