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Family Apocynaceae

Synonyms: Asclepiadaceae APNI*
Periplocaceae APNI*

Description: Trees, shrubs, climbers with twining stems or occasionally erect or trailing herbs; latex present, usually milky but sometimes watery.

Leaves simple, entire, opposite or whorled, rarely alternate; stipules absent.

Flowers in cymes or racemes or solitary in axils; bisexual, actinomorphic. Sepals 5, usually shortly fused, often with small glands inside near the base. Corolla tubular, 5-lobed; lobes spreading. Stamens 5, epipetalous; anthers enclosed in the corolla tube or exserted, free or cohering in a cone or ring around the style. Ovary superior or rarely half-inferior, carpels 2, either the carpels free but the styles fused and the placentas marginal, or the carpels fused, the ovary then either 2-locular with axile placentas or l-locular with 2 parietal placentas; ovules usually numerous, sometimes few; style usually dilated near the apex, the swollen style head sometimes adhering to the anthers; stigma not obvious, mostly on the undersurface of the style head.

Fruit a pair of follicles, drupes or berries (sometimes only 1 of the pair developing) or a single capsule, berry or drupe; seeds sometimes with a coma.

Distribution and occurrence: World: 380 gen., 4700 spp., mainly trop. & subtrop. regions. Aust.: 55 gen., c 200 spp., all States; mainly in rainforest in the east but some species widespread in arid areas.

External links:
Angiosperm Phylogeny Website (Family: Apocynaceae, Order: Gentianales)

Several species are sources of drugs used in medicine, including species of Rauvolfia which yields the alkaloid reserpine and Cerbera, Cascabela, Strophanthus and Nerium, from which cardiac glycosides are obtained. Many are toxic if ingested by animals (including humans); these include the ornamental Nerium oleander L. (Oleander) and Cascabela thevetia (L.) Lippold (Yellow Oleander). Some have been used as sources of rubber. Several are cultivated for their showy scented flowers; these include species of Allamanda, Mandevilla, Nerium, Plumeria, Cascabela, Trachelospermum and Vinca.

Text by G. J. Harden & J. B. Williams
Taxon concept:

Taxa not yet included in identification key
Acokanthera,    Orbea,    Stapelia

 Key to the genera 
1Pollen granular, not aggregated into pollinia2
Pollen aggregated into pollinia14
2Leaves alternate; shrub or small tree with yellow flowersCascabela
Leaves opposite or whorled; climbers, herbs, shrubs or trees; flowers either white or pink, or if yellow then plants climbing
                       Back to 1
3Plants with sharp, stiff spines at many nodes; shrubs or scrambling climbersCarissa
Plants without spines at nodes
                       Back to 2
4Erect plants, neither climbing nor trailing5
Climbers with twining stems, or trailers
                       Back to 3
5Herbs up to c. 70 cm high; flowers solitary in the axils and the corolla more than 20 mm diamCatharanthus
Shrubs or small trees more than 1 m high; flowers in cymes, the corolla usually less than 20 mm diam. or rarely more than 20 mm diam. (in Nerium)
                       Back to 4
6Fruit a drupe, less than 12 mm diam., orange or red, 1-seeded or 2–4-seeded and moniliform; leaves with apex spinose or blunt to mucronate, leaves usually less than 5 cm longAlyxia
Fruit either a follicle or drupaceous (and then more than 20 mm diam., red and 1–6-seeded, not moniliform); leaves not spinose, rarely blunt or mucronate, more than 5 cm long
                       Back to 5
7Leaves leathery; flowers more than 20 mm diamNerium
Leaves more or less soft; flowers less than 20 mm diam
                       Back to 6
8Fruit a cylindrical follicle, dry and pale brown when mature, 6–24 cm long; petiole slender, mostly 8–45 mm longAlstonia
Fruit narrow-ovoid to ovoid or ellipsoid, either drupaceous or tardily dehiscent, yellow-orange or red, more or less fleshy when mature, 2.5–8 cm long; petiole 1–12 mm long
                       Back to 7
9Main lateral veins of leaves subtransverse, regular, more than 11 pairs; intramarginal vein present; fruit a red drupe with 1–6 large seeds10
Main lateral veins of leaves oblique, irregular, less than 11 pairs; intramarginal vein absent; fruit banana-shaped, yellow-orange, fleshy but finally dehiscing to expose several seeds
                       Back to 8
10Fruit 2–3 cm long, endocarp without obvious cavities; seed single, central; leaves with lateral veins distinct on the upper surface, more or less obscure on the lower surfaceNeisosperma
Fruit 4–8 cm long, with 2 cavities and the seeds on a flattened placenta between the cavities; leaves with lateral veins prominent on the lower surface
                       Back to 9
11Flowers solitary in the leaf axils; corolla blue; low trailing herbaceous perennialVinca
Flowers in cymes or racemes; corolla white, yellow, orange or pink; climbers with twining stems
                       Back to 4
12Flowers more than 40 mm in diam., white, in racemes; ovaries free but style single in each flower; fruit a pair of follicles cohering at the tipMandevilla
Flowers less than 20 mm in diam., orange-yellow to creamy white, in cymes; ovary of 2 fused carpels, 1- or 2-locular; fruit a berry or a capsule separating when mature into 2 follicle-like segments
                       Back to 11
13Anthers included in the corolla tube, not fused; fruit a globose to ovoid or oblong berry; seeds several, embedded in pulp, lacking hairsMelodinus
Anthers partially or wholly exserted and fused or cohering in a cone or ring around the style head; fruit a capsule, separating into 2 follicle-like segments; seeds numerous, each with a tuft of long silky hairs
                       Back to 12
14Leafless scrambling or twining plants with long pale green succulent, jointed stemsCynanchum
Plants with well-developed leaves, stems neither succulent nor jointed
                       Back to 1
15Corolla sky-blue; corona of 5 erect dark blue ribbed segments, inserted on corolla tube, free from columnOxypetalum
Corolla and corona never blue; corona not as above
                       Back to 14
16Erect plants to 2 m high, neither twining nor trailing17
Climbers with twining stems or lax, trailing plants
                       Back to 15
17Flowers less than 6 mm diam., in compact umbels; corona segments small, not spreading; corolla urceolate, lobes spreadingMarsdenia
Flowers 8–15 mm diam., in loose umbels; corona segments large, sac-shaped or boat-shaped, spreading, conspicuous; corolla rotate, lobes reflexed
                       Back to 16
18Corolla red, corona yellow; corona segments with an erect or curved horn arising from inner face; follicle elongated, smoothAsclepias
Corolla and corona white; corona segments without a horn-like outgrowth; follicle soft, inflated, ovoid or globose with numerous soft, spine-shaped processes
                       Back to 17
19Leaves with (1 or) 2–25 minute raised glands in a cluster on upper surface of lamina at base of the midvein20
Leaves without raised glands at base of the midvein
                       Back to 16
20Stems and lower surface of leaves densely and softly pubescent with long pale or rusty hairs, young shoots furry21
Stems and leaves glabrous or finely pubescent with short pale hairs, young shoots not furry
                       Back to 19
21Hairs fawn or rusty; flowers more than 15 mm diam., in racemes on thick perennial pedunclesThozetia
Hairs pale or colourless; flowers less than 5 mm diam., in axillary panicles; peduncles not persistent
                       Back to 20
22Leaves very thick, fleshy but firm to rigid, faintly veined, broad-ovate to circular; corolla lobes valvate in bud; peduncles perennial, appearing as short thick spurs, with scars of flowers of earlier yearsHoya
Leaves thin or of moderate thickness, not rigid, mostly distinctly veined; corolla lobes contorted in bud; peduncles shed after flowering and fruiting
                       Back to 20
23Corona absent or segments adnate to lower part or base of the staminal column24
Corona of 5 segments arising from the base of the corolla tube, free from column
                       Back to 22
24Corona of 5 spreading fleshy obtuse knobs, fully fused to the column; pollinia globose, small, and laterally placed; flowers mostly purple to red (whitish in 1 species)Tylophora
Corona absent or of 5–20 segments or lobes, not knob-like, each with a free upper part and a fused lower part; pollinia elongated, not round, erect or pendent, not laterally placed; flowers mostly whitish or yellow
                       Back to 23
25Corona absent or lower part of corona segments with a free wing or with basal auricles or lobes; pollinia erectMarsdenia
Lower part of corona segments without a free wing or lobes or auricles, sometimes tubular at the base; pollinia pendent
                       Back to 24
26Leaves lanceolate to ovate or oblanceolate or oblong, more than 5 mm wide; corona of 5 segments27
Leaves linear, less than 5 mm wide; corona of 10 segments
                       Back to 19
27Leaves thin, soft, lanceolate to ovate, acute or acuminate at apex; pollinia erect, 4 per anther, 2 in each loculus; corona of 5 incurved horn-like segments shorter than column; flowers less than 5 mm diam., in many-flowered paniclesSecamone
Leaves thick, fleshy, firm to fairly stiff, mostly oblanceolate or oblong, apex abruptly pointed; pollinia pendent, 2 per anther, 1 in each loculus; corona of 5 erect segments with recurved tips, longer than column; flowers more than 10 mm diam., in few-flowered cymes
                       Back to 26

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