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(Last Modified On 5/30/2013)
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(Last Modified On 5/30/2013)
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Family
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ASCLEPIADACEAE
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Contributor
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DAVID L. SPELLMAN
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Description
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Mostly perennial herbs, vines, occasionally shrubs or small trees, some fleshy or cactus-like, generally with milky sap. Leaves opposite or whorled, simple, entire, sometimes caducous or vestigial, estipulate. Inflorescence generally cy- mose, the cymes usually umbelliform or racemiform, rarely paniculate. Flowers bisexual, actinomorphic, occasionally tending toward zygomorphy; calyx of 5 distinct or basally fused sepals which are imbricate or open in bud, generally with 1 or more glandular structures within the sinuses; corolla rotate, cam- panulate, urceolate, or funnelform, commonly white, pink, green, or brown- purple, shallowly or deeply 5-lobed, the lobes contorted or less commonly val- vate in bud, the tube sometimes terminated by the faucal annulus, a low ridge or ring of tissue; stamens 5, inserted at or near the base of the corolla, the fila- ments flattened and short, usually connate to form a tube which is united to the stigma to form the gynostegium, a corona usually present, simple or of 5 or more lobes, adnate to the corolla throat or free from it but originating from the filaments, its structure highly variable, the anthers introrsely 2-celled, rarely 4-celled, sometimes with a sterile dorsal appendage of variable form, the con- nective often apically produced into a thin membranous appendage; pollen rarely in tetrads (Periplocoideae), mostly agglutinated into waxy masses (pol- linia), these usually solitary in each anther cell and combined in pairs through a yoke mechanism consisting of a translator arm which connects each pollinium to a hardened black or brown ? trullate gland or corpusculum, the corpuscu- lum situated between the anthers and adnate to the stigma disc; ovary of 2 distinct carpels, superior and included within the staminal tube, styles 2, short and distinct but united at the stigma, the stigma 1, peltately dilated into a usually pentagonal disc which is apically flattened, depressed, convex, umbo- nate, or rostrate, the ovules numerous in each carpel, pendulous and imbricate upon the lateral placentae. Fruit usually a single follicle resulting from the abortion of one carpel, generally ovoid to somewhat fusifolmrn, the exocarp smooth or variously ornamented with tubercular or muricate projections, sometimes
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Habit
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herbs, vines, occasionally shrubs or small trees
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Description
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longitudinally winged, glabrous or pubescent, ventrally dehiscent; seeds com- pressed, usually with a marginate or emarginate wing, the seed coat thick or ? membranaceous, narrowed apically and usually bearing a tufted micropylar coma of long silky hairs; embryo large, the endosperm thin.
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Distribution
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The Asclepiadaceae are a large family of wide distribution in tropical and temperate areas.
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Note
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The complex structure of the flower has been used to divide the family into a large number of small, mostly indistinct genera. Various authors have recognized in excess of 250 genera and more than 1800 species on a world- wide basis. Woodson (1941), in an attempt to render order to the chaotic array of genera, reduced the North American representatives of the family to nine genera. In the New World, the Asclepiadaceae occupy nearly every type of habitat from Canada to southern Chile. The North American center of distribution of the family is southern Mexico and northern Guatemala, and the number of species becomes fewer as one goes south. Williams (1969) treated 90 taxa in the Flora of Guatemala, while in Panama, there are about half that number. Of the 43 taxa recognized in the present treatment, 12 are found elsewhere in Central and South America, 3 are known only from Mexico and Central Amer- ica, 9 are South American, 13 are endemic, and 2 are widespread throughout the tropics. Of the present endemic members, most are morphologically tied to the South American element of the family, and may eventually be recorded from there. All 9 of the genera recognized by Woodson for North America occur in Panama. Plants of this family are of little economic importance, except a few of horti- cultural use, most notably species of Hoya, Stephanotis, Stapelia, and Crypto- stegia. Young fruits of some species are used as vegetables, either cooked or fresh, in Central and South America. Many members of the family are toxic to humans and livestock. Because of the specialized characters involved in the identification of the Asclepiadaceae, three keys are included here. The first, based on natural char- acters following Woodson's (1941) concepts, is written to encompass the genera as they exist beyond the limits of Panama. An artificial key based solely on Panamanian material attempts to characterize the genera without reliance on more technical characters. The third key is based on fruiting characters of taxa occurring in Panama for which fruits are known.
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Reference
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Williams, L. 0. Flora of Guatemala. Fieldiana: Bot. 24, part VIII (4): 407- 472. 1969. Woodson, R. E., Jr. The North American Asclepiadaceae. I. Perspective of the genera. Ann. Missouri Bot. Gard. 28: 193-244. 1941.
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Key
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KEY TO THE GENERA-Based on natural characters. a. Pollen granular, united into tetrads, not agglutinated into sac-like pollinia; flowers 4 cm or more long, pink to purplish (Peri...... 1. Cryptostegia aa. Pollen agglutinated into sac-like pollinia; flowers 3 cm long or less, variously colored (Asclepiadoideae). b. Pollinia pendulous, their faces uniformly flattened or rounded, uniformly fertile up to the point of attachment of the translators (Asclepiadeae). c. Plants erect or nearly so, herbaceous, not scandent. d. Corolla rotate, lobed nearly to the base, the lobes strongly reflexed at an- thesis; corona of 5 cucullate hoods ...... 2. Asclepias dd. Corolla campanulate, lobed to about the middle, the lobes spreading; corona of 5 fleshy segments upturned at the base ...... 3. Calatropis cc. Plants scandent, herbaceous or somewhat woody. e. Translators conspicuously thickened and appendaged near their attachment to the corpusculum; corolla lobes linear, 15-20 mm long; leaves ovate- cordate ...... 4. Oxypetalum ee. Translators not conspicuously thickened or appendaged; corolla not linear, less than 15 mm long; leaves various. f. Corona of 5 separate, laminate scales, not inflated ...... 5. Cynanchum ff. Corona of 5 expanded bladder-like segments. g. Corona of 5 small semi-vesicular sacs not basally connate, attached separately to the backs of the anthers; plants glabrous; leaf bases generally rounded ...... 6. Blepharodon gg. Corona of 5 closed vesicles basally connate by a fleshy ring and at- tached separately to the backs of the anthers; plants glabrous or pubescent; leaf bases acute to truncate or cordate ...... 7. Sarcostemma bb. Pollinia horizontal or erect, their faces uniformly rounded and fertile to point of attachment of the translators or one or both faces indented, with a sterile hyaline margin near the point of attachment of the translators. h. Pollinia strictly erect, their faces uniformly rounded, uniformly fertile to the attachment of the translators (Tylophoreae). i. Corolla infundibular, urceolate, or campanulate, never strictly rotate nor waxy white in color. j. Corolla less than 10 mm long, usually red, green, or yellow 8. Marsdenia jj. Corolla much greater than 20 mm long, white ...... 9. Stephanotis ii. Corolla rotate, flowers in pedunculate umbels, waxy white in color 10. Hoya hh. Pollinia horizontal or nearly so, occasionally ascending or descending, but one or both faces indented, and with a sterile hyaline margin near the point of attachment of the translators (Gonolobeae). k. Corolla lobes conspicuously crispate; anthers conspicuously hypertrophied and vesicular throughout ...... 11. Fischeria kk. Corolla lobes not conspicuously crispate; anthers not conspicuously hyper- trophied and vesicular. 1. Anthers without dorsal appendages; pubescence usually of long brown hairs overtopping shorter bulbous ones (glabrous in M. mediocris) ...... 12. Matelea 11. Anthers with spreading + laminate, fleshy dorsal appendages; glabrous or pubescence not as above ...... 13. Gonolobus ARTIFICIAL KEY TO THE GENERA-Based on Panamanian material. a. Plants erect, not at all scandent or procumbent. b. Corolla campanulate, lobes purple tipped, not reflexed at maturity ...... 3. Calotropis bb. Corolla rotate, lobes red-orange or green, strongly reflexed at maturity ...... 2. Asclepias aa. Plants scandent, climbing or procumbent. c. Plants glabrous throughout or at least on the upper surface of the leaves. d. Leaf bases shallowly or deeply cordate. e. Inflorescences open, an elongate raceme or a large panicle of racemes ...... 5. Cynanchum ee. Inflorescences condensed, appearing umbellate, never paniculate. f. Leaves heart-shaped; corolla lobes orange-brown, reflexed ...... 12. Matelea ff. Leaves not heart-shaped; corolla lobes brownish-red or green, not reflexed. g. Flowers brownish-red, corolla tube evident ...... 8. Marsdenia gg. Flowers green, corolla rotate, the tube not evident without dissection. h. Flowers less than 1 cm wide ...... 13. Gonolobus hh. Flowers more than 2 cm wide ...... 12. Matelea dd. Leaf bases various but not cordate. i. Flowers large and showy, corolla tube more than 2 cm long; cultivated and escaping. j. Flowers pink to purple ...... 1. Cryptostegia jj. Flowers waxy white ...... 9. Stephanotis ii. Flowers smaller, corolla tube less than 1 cm long; cultivated or native. k. Flowers white (sometimes greenish tinged) or white with purplish blotches. 1. Flowers white with purple spots; corolla lobes linear ...... 8. Marsdenia 11. Flowers uniformly white; corolla lobes various but not linear. m. Corolla 5 mm or less in diameter ...... 5. Cynanchum mm. Corolla usually 10 mm or more in diameter. n. Thick coarse vines with thick leaves, flowers waxy white; cultivated species ...... 10. Hoya nn. Slender vines with thin leaves, flowers white but not waxy; native species. o. Inflorescence umbellate, 20- or more flowered ...... 7. Sarcostem m a oo. Inflorescence a contracted raceme, usually less than 10-flowered ...... 6. Blepharodon kk. Flowers variously colored, not white. p. Flowers brownish-red, distinctly tubular, in dense umbelliform clusters...... 8. Marsdenia pp. Flowers green or yellowish, tube distinct or inconspicuous, in few flowered contracted racemes or 2- to several-flowered umbelliform clusters. q. Flowers yellow to greenish yellow, with or without a distinct tube, in 2- to several-flowered umbelliform clusters ...... 8. Marsdenia qq. Flowers distinctly green, without a distinct tube, in few-flowered contracted racemes. r. Flowers 2 cm or more in diameter, corolla lobes spreading ...... 13. Gonolobus rr. Flowers less than 1 cm in diameter, corolla lobes reflexed ...... 12. Matelea cc. Plants distinctly pubescent, at least on the upper surfaces of the leaves. s. Plants with long, brown, spreading, multicellular hairs on stems and leaves, these usually dense on the younger stems. t. Corolla lobes contorted-crispate on the margins ...... 11. Fischeria tt. Corolla lobes never contorted-crispate at the margins ...... 12. Matelea ss. Plants without long, brown, spreading, multicellular hairs, pubescence usually whitish or buff. u. Leaf blades rounded at the base; flowers white ...... 7. Sarcostemma uu. Leaf blades cordate at the base; flowers greenish-yellow, or green. v. Corolla rotate, the tube not evident, less than 2 mm long ...... 13. Gonolobus vv. Corolla campanulate or with a distinct tube more than 5 mm long. w. Corolla campanulate, the lobes linear and ribbon-like ...... 4. Oxypetalum ww. Corolla tubular or rotate ...... 8. Marsdenia
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Key
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KEY TO SPECIES-Based mainly on fruiting material. a. Plants erect, follicles smooth. b. Fruits fusiform, attenuate apically, less than 2 cm in diameter ...... Asclepias curassavica bb. Fruits irregularly ovoid, not attenuate apically, more than 3 cm wide ...... Calotropis procera aa. Plants scandent, follicles smooth or variously appendaged. c. Follicles smooth, glabrous or pubescent, sometimes longitudinally striate, but not winged, ridged, or tuberculate. -+- fusiform. e. Leaves basally rounded; fruit 5-8 cm long, ca. 1.5 cm thick, apically acute ...... Sarcostemma clausum ee. Leaves basally cordate; fruit size variable, apically long acuminate. f. Fruit mostly less than 9 cm long, 2 cm thick ...... Sarcostemma bilobum ff. Fruit mostly more than 9 cm long, 2-3 cm thick ...... Oxypetalum cordifolium dd. Fruits glabrous or the pubescence minute and confined to the base and apex. g. Fruits usually paired, abruptly narrowed toward the apex, 5 cm long or less. h. Fruits ca. 5 cm long, 0.8 cm thick; inflorescences simple, umbellate ...... Cynanchum infimicola hh. Fruits 3-4 cm long, ca. 0.5 cm thick; inflorescences compound, a panicle of umbels ...... Cynanchum apocynellum gg. Fruits not paired, not abruptly narrowed toward the apex, more than 6 cm long. i. Fruits fusiform; leaves basally rounded. j. Fruits 15-20 cm long; stems with warty excrescences ...... Marsdenia rotheana jj. Fruits less than 10 cm long; stems not warty. k. Fruits 8-10 cm long, ca. 1 cm thick; stems and leaves glaucous ...... Sarcostemma glaucum kk. Fruits 6-9 cm long, ca. 1.5 cm thick; stems and leaves not glau- cous ...... Blepharodon mucronatum ii. Fruits ellipsoid to ovoid; leaves basally rounded to cordate. 1. Follicles ovoid, longitudinally striate, 12-16 cm long, 4.5-5 cm thick; leaves basally rounded ...... Marsdenia margaritaria 11. Follicles ellipsoid, not striate, 5-25 cm long, 2-10 cm thick; leaves basally cordate. m. Inflorescence a simple raceme or large panicle of racemes; leaves thin-succulent; follicles variable in size. n. Inflorescence racemose; follicles 5-10 cm long, 2-3 cm thick ...... Cynanchum magdalenicum nn. Inflorescence a panicle of racemes; follicles 15-21 cm long, 7-10 cm thick ...... Cynanchum cubense mm. Inflorescence a compact umbelliform cluster; leaves subcori- aceous; fruits 1.8-22 cm long, ca. 5 cm thick ...... Marsdenia maculata cc. Follicles with longitudinal wings, thick ridges, or with tuberculate or digitiform projections. o. Fruits glabrous, with 3-7 longitudinal wings, or a single cockscomb-like ridge at the base of the dorsal surface. p. Fruits ellipsoid, woody, with a thick, low, single dorsal ridge ca. 3 cm long near the insertion of the pedicel, 21-30 cm long, 9-12 cm thick ...... Matelea panamensis pp. Fruits ellipsoid to ovoid, woody or coriaceous, longitudinally 3-7 winged, less than 20 cm long, less than 5 cm thick. q. Fruits ellipsoid, the walls distinctly woody, with 4 wings running the length of the fruit; ca. 8 cm long, 2 cm thick ...... Cryptostegia madagascariensis qq. Fruits ellipsoid to ovoid, the walls thin and leathery, 3-7 winged; size various. r. Fruit with one dorsal and 2 lateral wings running the full length of the fruit, attenuate-ellipsoid, at least 5 cm long, 1 cm wide; stems glabrous ...... Gonolobus fuscoviolacells rr. Fruits 5- or 7-winged, attenuate-ovoid, 7-11 cm long, 2-3 cm wide; stems glabrous or long brown pubescent. s. Fruits with 2 full length lateral wings and a single dorsal wing ca. 3/4 the length of the fruit, ca. 7-8 cm long, 2-3 cm wide, stems glabrous ...... Matelea viridiflora ss. Fruits 7 winged, ca. 11 cm long, 3 cm thick; stems long, brown pubescent ...... Matelea trianae oo. Fruits pubescent, with tuberculate projections. t. Fruit ellipsoid-attenuate, with long finger-like tubercles, the pubescence of long, brown, septate hairs, 10-15 cm long, 2-3 cm wide ...... Matelea pinguifolia tt. Fruit ellipsoid, not attenuate, with short tubercles capped with light-colored corky tissue, the pubescence short, gray, nonseptate, ca. 8 cm long, 3 cm wide ...... Matelea maritima
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