APOCYNACEAE
NB The former family Asclepiadaceae (now known as Asclepiadoideae) is considered a subfamily of Apocynaceae and contains 348 genera. In this key there is a plant portrait for Asclepiadaceae. Periplocoideae are also considered a subfamily of the Apocynaceae. Both subfamilies may key out separately, all genera are taken up under Apocynaceae.
Morphological description
Woody, laticiferous, sometimes a climber with hooks (Willughbeia); no stipules but sometimes a ridge between leaves of one pair.
Leaves
Leaves usually decussate, but spirally arranged in Cerbera, Lepiniopsis, Plumeria*, Thevetia*, and whorled in Alstonia, some Alyxia, Dyera, and some Rauvolfia; simple, entire, penninerved, sometimes an intramarginal nerve and black glands underside of leaves (Chilocarpus, Leuconotis).
Inflorescence
Inflorescence sometimes leaf-opposed (Lepiniopsis).
Flowers
Corolla 4- or 5-me-rous, sympetalous, lobes contorted in bud, stamens 5, epipetalous, ovary superior, 2-locular; anthers fused with stigma, stigma club-shaped, hairs or scales in corolla throat.
Fruits
Fruit of 2, often separate, carpels. Carpels moniliform in Alyxia, Urceola; fruit spiny in Allamanda*
Seeds
Seeds many, often with a tuft of hairs.
Different from: (Apocynaceae s.s.) Asclepiadoideae: mostly herbaceous climbers, often trichomes at base of leaf blade, corolla star-shaped or urceolate, seeds usually flat. — Loganiaceae: no milk sap, interpetiolar stipules.
Distribution: The family is widespread in tropics and warm temperate zone. In Malesia c. 50 genera, mainly in tropical lowland rain forest, incl.: - Alstonia (pantropical), trees, lowland rain forest; - Alyxia (paleotropical), climbers and shrubs, lowland and montane rain forest; - Cerbera (paleotropical), trees, coastal forest; - Dyera (West Malesia), trees; lowland rain forest and swamp forest; - Kopsia (Indo-Malesia), shrubs and trees, rain forest; - Parsonsia (Indo-Australia) climbers, rain forest; - Rauvolfia (pantropical), shrubs and trees, lowland and lower montane rain forest and monsoon forest; - Tabernaemontana (pantropical), shrubs and trees, mostly lowland rain forest; - Willughbeia (Indo-Malesia), climbers, lowland rain forest; - Wrightia (paleotropical), trees; mostly seasonal forest.
Notes: Fruits water-dispersed: Cerbera, Ochrosia; wind dispersed: Alstonia, Dyera; animal-dispersed: Willughbeia. — Ornamentals: Allamanda*, Carissa, Catharanthus*, Cerbera, Kopsia, Nerium*, Tabernaemontana, Thevetia*, Wrightia. — Edible fruit: Carissa, some Willughbeia. — Medicinal: Alstonia, Catharanthus*, Rauvolfia. — Latex used to prepare chewing gum: Dyera. — Timber: Alstonia, Dyera.
Literature: C.A. Backer & R.C. Bakhuizen van den Brink, Fl. Java 2 (1965) 218-244; T.C. Whitmore, Tree Fl. Mal. 2 (1973) 3-24. — Dr. A.J.M. Leeuwenberg (WAG) is coordinating the revision of Malesian Apocynaceae.
Spot characters (Van Balgooy): All Apocynaceae: plants with white or yellow sap, broken leaves with white thread (p.p.), leaf with domatia (p.p.), corolla/petals with appendages (p.p.), apocarpous (p.p.), seeds comose (p.p.), seeds arillate (p.p.).
Other spotcharacters: Swollen stems: Adenium, Alstonia pneumatophora - Climbers with hooks/tendrils: Willughbeia - Climbers without hooks/tendrils: Aganosma, Alyxia, Amphineuron, Anodendron, Baharuia, Beaumontia, Carruthersia, Chilocarpus, Chonemorpha, Cleghornia, Cynangum, Dischidia, Ecua, Epigynum, Eucorymbia, Hoya, Ischnocarpus, Leuconotis, Marsdenia, Melodinus, Micrechites, Papuechites, Parsonsia, Pottsia, Strophanthus, Trachelospermum, Urceola, Vallaris, Vallariopsis - Climbers with opposite leaves: Aganosma, Alyxia (p.p.), Amphineuron, Anodendron, Baharuia, Carruthersia, Chilocarpus, Chonemorpha, Cleghornia, Clemensiella, Cryptolepis, Cynanchum, Dischidia, Ecua, Epigynum, Eucorymbia, Finlaysonia, Gymnanthera, Heterostemma, Hoa, Ichnocarpus, Leuconotis, Marsdenia, Melodinus, Micrechites, Myriopteron, Papuechites, Parsonia (Artia p.p.), Pottsia, Pycnorhachis, Sarcolobus, Secamone, Spirolobium, Stephanotis, Streptocaulon, Strophanthus, Telosma, Trachelospermum, Urceola, Vallariopsis, Willughbeia, Zygostelma - Armed plants: Carissa – Ant plants: Dischidia (p.p.), Hoya (p.p.) – Winged stems (stems with ridges/flanges): Heterostemma cuspidatum, Secamone elliptica – Wave-like sympodial branching: many genera, e.g., Alstonia, Kopsia – Proleptic shoots: e.g., Alstonia - Dried plants resinous: Alstonia (p.p.), Dyera (p.p.), Rauvolfia (p.p.) – Crushed leaves smell of fenugreek: Tylophora cissoides (p.p.) – Interpetiolar stipules/stipule-like structures: many taxa have ridges, e.g., Cynanchum(p.p.), Mandevilla, Micrechites, (Lamechites), Myriopteron(p.p.), Tabernaemontanum - Leaves spiral in opposite-leaved families: Adenium, Cerbera, Lepinia, Lepiniopsis, Plumeria, Thevetia - Leaves verticillate/whorled: Allamanda, Alstonia, Alyxia (p.p.), Asclepias, Cerbera (rosettes), Dyera, Hoya (p.p.), Melodinus (p.p.), Nerium, Ochrosia (p.p.), Parsonsia (p.p.), Rauvolfia, Wrightia (p.p.) - Leaves anisophyllous: Alyxia (p.p.) – Triplinerved leaves: Hoya (p.p.) - Intramarginal vein: Amphineuron, Chilocarpus, Cleghornia, Leuconotis - Secondary venation parallel: Alstonia, Alyxia (p.p.), Ochrosia (p.p.) - Drying leaves turn black: Cerbera, Voacanga – Leaves withering red: Kopsia arborea – Leaves glaucous: some taxa, e.g., Alyxia (p.p.), Anodendron (p.p.), Dyera(p.p.), Willughbeia (p.p.) – Bullate leaves: Dischidia (p.p.), Willughbeia anomala – Laminar or petiolar glands: Anodendron (p.p.), Chilocarpus (lamina), Leuconotis (lamina), Tylophora biglandulosa – Puncticulate leaf surface: Anodendron (p.p.), Chilocarpus, Leuconotis – Plants flowering when leafless: Cynanchum, (Sarcostemma) - Inflorescence leaf-opposed: Lepiniopsis – Compact inflorescence: Dischidia (p.p.), Hoya (p.p.), Marsdenia (p.p.), Parsonsia (p.p.) - Inflorescence a condensed raceme: Hoya (p.p.), Kopsia (p.p.) - Corolla/petals fimbriate or bifid: Hoya (p.p.), Ichnocarpus (p.p.) - Flowers yellow: Allamanda (p.p.), Anodendron, Hoya (p.p.), Leuconotis, Thevetia - Stamens with appendages: Cleghornia, Urceola - Anthers basifixed, apical pores: Wrightia - Fruit blue: Alyxia, Cerbera floribunda, Lepiniopsis – Woody fruits with scattered seeds: Chilocarpus (p.p.), Leuconotis, Melodinus, Voacanga, Willughbeia - Fruit spiny or muricate: Allamanda, Asclepias (p.p.), Asterostemma, Chilocarpus tuberculatus, Cynanchum, Parsonsia oligantha - Winged fruit: Marsdenia (p.p.), Myriopteron – Ridged fruit: Dregea, Finlaysonia, Ochrosia (p.p.), Tabernaemontana (p.p.) - Fruit moniliform: Alyxia (p.p.), Baharuia, Chilocarpus p.p.), Urceola, Pottsia – Winged seeds: some taxa, e.g., Dyera, Sarcolobus - Ruminate endosperm: Alyxia, Lepiniopsis, Tabernaemontana,
Illustrations: Fig. 9 & 10. C.A. Backer & R.C. Bakhuizen van den Brink, Fl. Java 2 (1965) 218-244; T.C. Whitmore, Tree Fl. Mal. 2 (1973) 3-24.
Image in PhytoImages for Apocynaceae