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APOCYNACEAE DOGBANE FAMILY

Thomas J. Rosatti, except as noted

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[10], 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

ASCLEPIAS MILKWEED

Thomas J. Rosatti & Carol A. Hoffman

Annual, perennial herb, shrub. Stem: prostrate to erect. Leaf: generally opposite (alternate, whorled), each pair at right angles to those below, above, generally persistent; blade narrow-linear to ovate or cordate. Inflorescence: terminal or at generally upper nodes, umbel-like cyme. Flower: ring of tissue at base of corolla 0; filament column appendages (hoods) free, elevated above corolla base or not, each often with an elongate projection (horn) attached to inside, margins converging and meeting or nearly meeting adaxially but not fused; anthers fused into anther head around and fused to pistil head, pollen in pollinia; pistil head flat or conic on top; nectaries in stigmatic chambers. Fruit: erect (but generally on pendent pedicel) or pendent, lance-ovoid to ovoid, smooth or with tubercles.
In narrow sense of genus, 100 species: North America, Central America, perhaps South America. (Greek physician Aesculapius) Fresh flowers generally better for determining relative positions of parts; hoods may have near anther head 2 ± sickle shaped lobes each that may ± resemble horns. A. linaria not outside cultivation in California, so deleted here; previous inclusion in TJM2 (2012) based on faulty locality data.
Unabridged references: [Liede-Schumann & Meve 2006 http://www.uni-bayreuth.de/departments/planta2/research/databases/delta_as/www/asclep.htm; Woodson 1954 Ann Missouri Bot Gard 41:1–211]

Key to Asclepias

A. fascicularis Decne. NARROW-LEAF MILKWEED
NATIVE
Perennial herb, generally glabrous. Stem: ascending to erect. Leaf: opposite (and reduced, on sterile branches) or whorled generally in 3s to 5s, often with clusters of smaller leaves in axils; petiole short; blade narrow-lanceolate, base tapered. Inflorescence: terminal and at upper nodes; peduncle 1–3(5) cm. Flower: corolla reflexed, green-white, purple-tinged or not; hoods elevated above corolla base, generally exceeded by anther head, green-white; horns exserted, generally exceeding hoods (and anther head). Fruit: erect on erect pedicels. Seed: 5.5–7 mm.
2n=22. Dry ground, valleys, foothills; 50–2200 m. California (except North Coast, Central Coast, South Coast); to Washington, Utah, Baja California. Generally poisonous to stock. May–Oct [Online Interchange]

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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. Asclepias, Revision 1, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=14375, accessed on Jul 29 2014

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click for enlargement Asclepias fascicularis
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© 2003 Christopher L. Christie

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Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.