27. Ipomoea carnea subsp. fistulosa (Martius ex Choisy) D. F. Austin, Taxon. 26: 237. 1977.
树千牛 shu qian niu
Ipomoea fistulosa Martius ex Choisy in A. de Candolle, Prodr. 9: 349. 1845; Batatas crassicaulis Bentham; I. crassicaulis (Bentham) B. L. Robinson.
Shrubs, 1-3 m; axial parts puberulent, later glabrescent; sap milky. Branches terete or angular, stout, becoming sparsely lenticellate with age. Petiole 2.5-15 cm; leaf blade ovate or ovate-oblong, 6-25 X 4-17 cm, densely puberulent or adaxially subglabrous, base cordate or truncate, margin entire, apex acuminate, mucronulate; midvein 2-glandular abaxially at base, lateral veins 7-9 pairs. Inflorescences few to several flowered; peduncle stout, 5-10 cm; bracts early deciduous, ovate. Pedicel 1-1.5 cm. Sepals ovate or nearly circular, broadly rounded, abaxially puberulent, equal or inner ones longer, 5-6 mm. Corolla lilac or pink, darker inside, funnelform, 7-9 cm; tube and midpetaline bands mealy outside. Stamens included; filaments unequal; anthers linear, base sagittate. Pistil included; ovary puberulent. Style base puberulent; stigma 2-lobed. Capsule pale brown, ovoid, 1.5-2 cm, 4-valved, apiculate. Seeds black, ca. 1 cm, brown sericeous-pubescent. 2n = 30.
Guangxi, Hainan, Taiwan [Cambodia, India, Indonesia, Japan (Ryukyu Islands), Myanmar, Nepal, New Guinea, Pakistan, Sri Lanka, Thailand; North America, Pacific Islands, South America]
Ipomoea carnea, which is native of tropical America, is cultivated in many parts of Asia and has become widely naturalized. The ± erect, shrubby subsp. fistulosa is preferred in cultivation, whereas subsp. carnea, which is more viny, is seldom seen outside its native range in Central and South America.