泽兰族 ze lan zu

Authors: Yilin Chen, Takayuki Kawahara & D. J. Nicholas Hind

Herbs (rarely aquatic or semiaquatic), subshrubs, shrubs, climbers, small trees, sometimes epiphytic. Leaves usually opposite, rarely strictly alternate, sometimes rosulate or verticillate, sessile or petiolate, blade usually simple. Synflorescence usually a corymbose panicle, sometimes spicate. Capitula sessile or distinctly pedunculate, homogamous, discoid, rarely with some zygomorphic outer florets; involucre cylindric, campanulate, or hemispheric, rarely subtended by a subinvolucral bract; phyllaries in 1 to several series, few or numerous, imbricate, subimbricate, or distant, equal, subequal, or markedly graded, persistent or variously deciduous, lanceolate or ovate; receptacle flat to convex, sometimes highly conical, usually naked, glabrous or sometimes pubescent. Florets few, very rarely 1, often 4 or 5 to many, commonly fragrant; corollas funnelform to tubular, never truly yellow; lobes relatively short, commonly 5, very rarely 4; anther cylinders usually included within corolla tube; anther appendages obtuse or acute, rarely emarginate or lobed, as long as broad or shorter, sometimes absent, basal appendages short or almost absent, obtuse or rounded; antheropodia indistinct, cylindric or variously pronounced; nectary rarely visible; style base glabrous or pubescent, sometimes with a swollen node; styles usually very conspicuous and much exserted, glabrous or rarely pubescent; style branches linear to clavate, obtuse, stigmatic surfaces variously papillate. Achenes obovoid or oblong with phytomelanin in achene walls, usually 3-5(or 10)-ribbed, body rarely flattened with 2 ribs or 5 winged ribs, sometimes glandular, glabrous or variously setuliferous; carpopodium often paler than achene body, rarely indistinct or absent, of several layers of variously enlarged, sometimes ornamented cells, usually symmetrical, rarely eccentric, annular, cylindric, or stopper-shaped; pappus sometimes absent and reduced to an apical callus, rarely a laciniate crown, or vestigial, occasionally coroniform, usually of setae, commonly uniseriate, rarely biseriate or very rarely multiseriate, usually persistent, sometimes fragile, usually numerous, sometimes few, usually equal or subequal, rarely very short, or occasionally of flattened scales or awnlike scales, rarely of two distinct elements, very rarely of broad laciniate setae, or of few clavate apical appendages; setae commonly barbellate or laciniate, rarely plumose, apices acute or obtuse, usually gradually tapering, sometimes dilated, very rarely conspicuously narrowing.

About 180 genera and ca. 2,000 species: concentrated in Mexico and Central and South America, with relatively few native species in the Old World; several pantropical weeds widespread in the Old World; ten genera (seven introduced) and 25 species (six endemic, nine introduced) in China.

The tribe appears to be nearly restricted to the W Hemisphere, suggesting a Neotropical origin. The subtribes show a mixed distribution pattern, with explosive speciation in several, especially those occurring in Brazil, the Caribbean, Colombia, and Mexico. There are many pantropical and pansubtropical weeds in the tribe. Uses of members of the tribe have been briefly summarized by King and Robinson (Monogr. Syst. Bot. 22: 1-581. 1987). More recent references on the topic include S. Garg and T. C. S. Sastry (in P. D. S. Caligari & D. J. N. Hind, Compositae Biol. Utiliz. 2: 361-382. 1996; Ageratum conyzoides, Mikania micrantha), Y. P. Huang and Y. R. Ling (in P. D. S. Caligari & D. J. N. Hind, loc. cit.: 431-451; Ageratum houstonianum, Adenostemma), M. Heinrich (in P. D. S. Caligari & D. J. N. Hind, loc. cit: 475-503; 31 Mexican species), and J. Vallès et al. (in P. D. S. Caligari & D. J. N. Hind, loc. cit.: 453-466; Eupatorium cannabinum). Stevia rebaudiana (Bertoni) Hemsley, a native of Paraguay, is cultivated in China as the source of a strong sweetener and sugar substitute.

See also Hind and Robinson (in Kadereit & C. Jeffrey, Fam. Gen. Vasc. Pl. 8: 510-574. 2007).