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Key to families | Table of families and genera
Indexes to all accepted names and synonyms:
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Annual, perennial herb, shrub, tree, often vine; sap generally milky. Leaf: simple, alternate, opposite, subwhorled to whorled, entire; stipules 0 or small, finger-like. Inflorescence: axillary or terminal, cyme, generally umbel- or raceme-like, or flowers 1–2. Flower: bisexual, radial; perianth parts, especially petals, overlapped, twisted to right or left, at least in bud; sepals generally 5, fused at base, often reflexed, persistent; petals generally 5, fused in basal ± 1/2; stamens generally 5, attached to corolla tube or throat, alternate lobes, free or fused to form filament column and anther head, filament column then generally with 5 free or fused, ± elaborate appendages abaxially, pollen ± free or removed in pairs of pollinia; nectaries 0 or near ovaries, then 2 or 5, or in stigmatic chambers; ovaries 2, superior or ± so, free [fused]; style tips, stigmas generally fused into massive pistil head. Fruit: 1–2 follicles, (capsule), [berry, drupe]. Seed: many, often with tuft of hairs at 1 or both ends.
200–450 genera, 3000–5000 species: all continents, especially tropics, subtropical South America, southern Africa; many ornamental (including Asclepias, Hoya, Nerium, Plumeria, Stapelia); cardiac glycosides, produced by some members formerly treated in Asclepiadaceae, used as arrow poisons, in medicine to control heart function, and by various insects for defense. [Fishbein 2001 Ann Missouri Bot Gard 88:603–623] Asclepiadaceae ("asclepiads"), although monophyletic, included in Apocynaceae because otherwise the latter is paraphyletic. Complexity of floral structure, variation in asclepiads arguably greatest among all angiosperms. Pattern of carpel fusion (carpels free in ovule-bearing region, fused above), present ± throughout Apocynaceae (in broad sense), nearly unknown in other angiosperms. Base chromosome number generally 11; abundance of latex, generally small size of chromosomes evidently have impeded cytological investigations. —Scientific Editor: Bruce G. Baldwin.
Unabridged references: [Civeyrel et al. 1998 Molec Phylogen Evol 9:517–527; Rosatti 1989 J Arnold Arbor 70:307–401]
Key to Apocynaceae
Perennial herb, erect, semi-woody. Leaf: alternate to subwhorled. Inflorescence: ± terminal, compound cyme. Flower: corolla salverform; filaments free, attached near top of corolla tube, unappendaged, anthers free from each other and stigma, pollen ± free; nectary 0 or a shallow ring around ovaries; style ± thread-like, stigma skirted at base. Seed: glabrous.
5–25 species: North America, Japan. (John Amson, Virginia physician, 18th century)
Unabridged references: [McLaughlin 1982 Ann Missouri Bot Gard 69: 336–350]
Plant glabrous or gray-tomentose. Stem: several to many from woody crown, 16–36 cm, branches few to many. Leaf: 2–4 cm; petiole short or 0; blade ovate-lanceolate, acute at both ends. Flower: calyx lobes erect, thread-like above base; corolla ± white, blue, or ± green, tube ± 15 mm, inflated above middle, narrowed just below spreading lobes; style with spheric thickening just below stigma. Fruit: 3–8 cm, constricted between seeds, often breaking into 1-seeded segments.
2n=22. Desert plains, canyons; 300–1800 m. San Bernardino Mountains (n slope), Desert; to Utah. Tomentose and glabrous plants (latter assignable to Amsonia brevifolia A. Gray) have identical ranges, do not intergrade, and show no other differences, suggesting hairiness is governed by a single gene. Mar–May [Online Interchange]
Previous taxon: Amsonia
Next taxon: Apocynum
Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Jul 29 2014
Citation for this treatment: [Author of taxon treatment] 2013. Amsonia, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=13179, accessed on Jul 29 2014
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© 2006 Steve Matson
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