a	Anthers adnate or ± adherent to style head Corolla lobe aestivation in bud typically dextrorse or valvate, rarely sinistrorse Fruit dehiscent, almost always apocarpous, a pair of follicles, sometimes reduced to one by abortion or postgenitally fused Seeds small, compressed, almost always with a coma (tuft of hairs) at one end
	b	Anthers free from style head Corolla lobe aestivation in bud typically sinistrorse (overlapping to the left), rarely dextrorse (overlapping to the right) Fruit dehiscent or indehiscent, syncarpous or apocarpous, a berry, drupe, follicle or capsule Seeds naked, with wings, or arils, but almost never with a tuft of hairs

	a	Anthers 2- or 4-locular, adnate to style head (if adherent by hairs or secretions then pollen gathered in 4 small pollinia - Secamonoideae), fertile throughout Filaments free or fused Pollen shed in tetrads into translators or gathered in 2(4) pollinia attached to the corpuscle Nectaries located in alternistaminal troughs at base of filaments or staminal column
	b	Anthers 4-locular, adherent to style head by hairs or secretions, lower part often sterile Filaments free Pollen shed as monads Nectaries, if present, in a ring around base of ovary

	a	Pollen gathered in pollinia attached in pairs (or 4s) to a ± spherical corpuscle which can become attached to a pollinator for removal Anthers 2- or 4-locular
	b	Pollen shed in tetrads into spoon-shaped translators with a sticky end which can adhere to a pollinator for removal Anthers 4-locular

	a	Anthers 4-locular Pollen gathered in 4 small pollinia attached to a soft, pale corpuscle	Secamone
	b	Anthers 2-locular Pollen gathered in 2 pollinia attached to a dark, hard corpuscle

	a	Ovary entire
	b	Ovary of 2 separate or almost separate carpels

	a	Ovary 2-locular, with 1-4, rarely many, ovules in each Shrubs or trees, rarely scandent
	b	Ovary 1(2)-locular, with many ovules Woody climbers or rarely shrubs

	a	Unarmed shrubs or trees Inflorescence axillary	Acokanthera
	b	Armed shrubs, sometimes scandent Inflorescence terminal or pseudo-axillary	Carissa

	a	Inflorescence of elongate, branched, terminal panicles	Ancylobothrys
	b	Inflorescence contracted, short and often clustered, terminal or axillary	Landolphia

	a	Stems subherbaceous, not taller than 1.5 m	* Catharanthus
	b	Stems woody Shrubs, trees or climbers

	a	Fruit baccate or drupaceous
	b	Fruit follicular

	a	Fruit a drupe Ovules 2 in each carpel	Rauvolfia
	b	Fruit baccate Ovules many in each carpel

	a	Calyx with distinct tube which is circumscissile at base	Voacanga
	b	Calyx divided almost to base

	a	Fruit of 2 large, subglobose mericarps Corolla tube shorter than 10 mm	Tabernaemontana
	b	Fruit syncarpous, bilobed Corolla tube longer than 10 mm	Callichilia

	a	Ovules many in each carpel Leaves oblong to oblanceolate Fruit longitudinally striate	Gonioma
	b	Ovules 2-4 in each carpel Leaves usually broadly ovate-elliptic Fruit lenticellate	Diplorhynchus

	a	Leaves opposite or ternate Stems woody or subherbaceous
	b	Leaves alternate or fascicled Stems succulent

	a	Corolla ± salver-shaped
	b	Corolla tube campanulate to broadly funnel-shaped

	a	Corolla without appendages in throat Leaves broadly elliptic	Holarrhena
	b	Corolla with scales or appendages in throat Leaves lanceolate, oblong or oblanceolate

	a	Woody climbers Leaves oblong to oblanceolate scales in corolla throat free	Oncinotis
	b	Trees or shrubs Leaves lanceolate Scales in corolla throat forming a short corona	Wrightia

	a	Corona absent	Baissea
	b	Corona present

	a	Corona reduced to paired appendages alternating with corolla lobes	Strophanthus
	b	Corona of 5 truncate epipetalous parts, each 3-8-lobed	* Nerium

	a	Stipules minute or absent Anthers produced into long, hairy appendages	Adenium
	b	Stipules transformed into rigid spines Anthers with only a short, terminal appendage	Pachypodium

	a	Gynostegium exserted from the corolla mouth
	b	Gynostegium enclosed in the corolla tube

	a	Corolla campanulate with distinct tube Erect, prostrate or climbing herbaceous geophytes with suffrutescent stems	Raphionacme
	b	Corolla rotate with tube indistinct Woody lianes with perennial stems

	a	Corona lobes broadly ovate Stems with interpetiolar, frill-like stipules	Mondia
	b	Corona lobes filiform Stems with interpetiolar lines or dentate ridges

	a	Corolla lobes narrowly triangular to triangular-ovate with acuminate apex Leaves glabrous, glossy	Petopentia
	b	Corolla lobes broadly ovate to oblong-ovate with obtuse apex Leaves adaxially glabrous to puberulous, abaxially tomentose	Tacazzea

	a	Corona lobes arising at the middle or lower down on the corolla tube	Cryptolepis
	b	Corona lobes arising at corolla mouth

	a	Corolla trumpet-shaped, pale green to yellow Corona lobes subulate Anthers hairy	Ectadium
	b	Corolla broadly campanulate, creamy white with centre maroon to violet Corona lobes clavate Anthers glabrous	Stomatostemma

	a	Pollinia developing in part of anther above position of corpuscle
	b	Pollinia developing in part of anther below position of corpuscle

	a	Pollinia without insertion crest
	b	Pollinia with insertion crest (ridge along edge of pollinium that becomes lodged in guide rail and through which pollen tubes arise)

	a	Carpels narrowing gradually into slender neck below style head Anther appendages with basal horizontal slit
	b	Style head sessile on carpels that lack slender neck Anther appendages without basal horizontal slit

	a	Corona absent on staminal tube Plant with clear sap
	b	Corona present on staminal tube Plant with clear or milky sap

	a	Corolla lobes closing tube at bases or remaining closed over mouth of tube Anther appendages covering whole of style head, mostly with apical tuft of hairs	Microloma
	b	Corolla lobes not closing corolla tube Anther appendages only covering base of style head, without apical tuft of hairs	Astephanus

	a	Style head produced beyond anthers into elongated cone bifid near apex Corona lobes behind anthers with margins folded backwards
	b	Style head and corona not as above

	a	Corolla less than 10 mm in diameter, tube not swollen towards base Plant with clear sap	Oncinema
	b	Corolla more than 15 mm in diameter, tube swollen towards base Plant with milky sap	* Araujia

	a	Corona consisting of 20 free lobules of ± equal length and 5 slightly shorter lobules adpressed to backs of anthers Pollinarium with caudicles rising up alongside corpuscle and then spreading and descending to pollinia Small erect herbs with clear sap	Eustegia
	b	Corona not as above Caudicles spreading and descending to pollinia If small erect herb then with milky sap

	a	Corona consisting of ± uniformly tall outer series of fused lobes encircling gynostegium, often with inner series of 5 lobes adpressed to backs of anthers
	b	Corona consisting of very small lobes beneath guide rails (sometimes absent) and very much larger (usually heavily vascularised) lobes behind anthers, these often with adaxial outgrowths or keels spreading towards style head

	a	Outer coronal series ± cupular near base of gynostegium, much shorter than and separated from inflated vesicular inner lobes adpressed to backs of anthers	Sarcostemma
	b	Outer coronal series cupular to tubular, sometimes divided nearly right to base but equalling or exceeding gynostegium, fused to inner lobes if these present	Cynanchum

	a	Stems twining
	b	Stems erect, decumbent or prostrate, mainly herbaceous Rootstock often tuberous

	a	Corolla with microscopic hairs inside, ± entirely without tube Corona ± absent beneath guide rails, lobes behind anthers with incurved margins Pollinia attached by slender caudicles, without insertion crest	Pentarrhinum
	b	Corolla with conspicuous hairs towards edges of lobes, with cupular tube below insertion of corona Corona with 5 discrete lobes beneath guide rails, lobes behind anthers without incurved margins Pollinia attached by caudicles much shorter than broad, with insertion crest along inner edge	Pergularia

	a	Anther appendages ascending and covering style head Style head conical above	Stenostelma
	b	Anther appendages adpressed to sides of style head but not covering it Style head concave above with slight central depression

	a	Pollinaria with very ornate caudicles considerably longer and broader than pollinia	Stathmostelma
	b	Pollinaria with caudicles much shorter and narrower than pollinia

	a	Corona (behind anthers) arising from staminal tube but fused to corolla tube for considerable distance towards sinuses of corolla lobes	Parapodium
	b	Corona (behind anthers) arising from staminal tube and not fused to corolla tube

	a	Corona lobes (behind anthers) fleshy and solid, without keel or process on ventral surface	Xysmalobium
	b	Corona lobes (behind anthers) dorsiventrally flattened or with margins folded inwards

	a	Corona lobes (behind anthers) dorsiventrally flattened, lateral margins not folded inwards to form cavity, sometimes keeled adaxially
	b	Corona lobes (behind anthers) flat, with lateral margins folded forwards at least in part (usually strongly) to form cavity (i.e. cucullate or complicate), with or without processes within cavity

	a	Corona lobes (behind anthers) spreading horizontally or curving outwards from base, with keels on inner face Usually fairly robust perennials	Pachycarpus
	b	Corona lobes (behind anthers) erect from base

	a	Petals white, flowers rather showy, in few-flowered, terminal umbels Corona lobes linear-oblong, purple Somewhat delicate perennial herbs	Fanninia
	b	Petals rarely white Corona lobes not as above

	a	Corona lobes (behind anthers) deeply trifid or quadrate with square shoulders, with an incurved midlobe and incurved margins at base ascending the column as narrow wings Usually single-stemmed perennial herbs	Woodia
	b	Corona lobes ± spathulate or lanceolate, sometimes produced into a point, usually keeled or with processes on inner surface

	a	Flowers in dense, globose, pedunculate heads Corolla lobes suberect, corona lobes spathulate or hastately subspathulate, usually with 2 keels capped by a transverse ridge or tubercle on inner face
	b	Flowers in sessile or pedunculate umbels Corona lobes often produced into a subulate or filiform apex, usually with 2 keels and frequently with 1 or 2 appendages on inner face

	a	Corona lobes hastately subspatulate Marsh-loving	Cordylogyne
	b	Corona lobes spatulate Slender grassland herbs	Periglossum

	a	Inflorescence pedunculate (except in S. bidens subsp. pachyglossum) Pollinia medially attached to caudicle with pellucid zone on outer side	Schizoglossum
	b	Inflorescence sessile Pollinia subapically attached, usually without germination zone (if this present then located at point of attachment of pollinia to caudicle)

	a	Corona lobes fleshy Pollinia without pellucid zone	Miraglossum
	b	Corona lobes thin Pollinia often with pellucid zone	Aspidoglossum

	a	Axils of leaves with minute bristles Flowers developing in gradual succession, spirally arranged around elongating top of peduncle	Kanahia
	b	Axils of leaves without bristles Inflorescences umbellate (flowers radiating from single point) with flowers all opening ± simultaneously

	a	Plants forming shrub or tree 2-8 m tall with cork-like bark and woody trunk, bearing inflated, ± smooth fruit 70-100 × 60-70 mm	* Calotropis
	b	Plants smaller, without woody trunk Fruit < 60 mm long and often covered with soft bristles

	a	Robust shrubs with many erect perennial branches Rootstock consisting of fibrous roots only, spreading just below surface	Gomphocarpus
	b	Few- to single-stemmed herbs with branches dying back to ground level in dry season Rootstock thickened below surface (often well below) and often forming tuber

	a	Plants consisting of a single slender, erect stem with linear to narrowly elliptic leaves
	b	Plants with several stems, stout and erect or decumbent and then erect

	a	Inflorescences 1-3 per plant at apex of stem	Aspidonepsis
	b	Inflorescences more than 3 per stem, spread over upper half of stem	Aspidoglossum

	a	Stems strictly erect Leaves glabrous and glaucous Inflorescence nodding	Gomphocarpus
	b	Stems initially horizontally spreading, then ascending Leaves scabrid and not glaucous Inflorescences erect	Asclepias

	a	Pollinia attached directly to corpuscle (without caudicles) Corona forming cylindrical tube around gynostegium Anthers with conspicuous erect and much inflated appendages filling up inside of tubular corona	Fockea
	b	Pollinia with slender to stout caudicles attaching them to corpuscle Corona consisting only of small lobes behind anthers Anthers with appendages adpressed to style head

	a	Corona on staminal column absent
	b	Corona on staminal tube present

	a	Corona on corolla tube present as pubescent ridges with inward-directed tips	Marsdenia
	b	Corona on corolla tube absent	Rhyssolobium

	a	Erect stiff shrubs Carpels with 2 ovules	Stigmatorhynchus
	b	Subshrubs or climbers, sometimes woody Carpels with few to many ovules

	a	Anther appendages small or obsolete
	b	Anther appendages elongate, membranous, incumbent on style apex or applied to side of conical tip or beak

	a	Corolla saucer-shaped, with broadly campanulate tube, crimson or black	Sphaerocodon
	b	Corolla almost flat, with obsolete tube and usually slender lobes, not crimson or black	Tylophora

	a	Corolla tube constricted at mouth Corona lobes broad and ± rectangular with subulate process adpressed to backs of anthers	Telosma
	b	Corolla tube not constricted at mouth Corona lobes narrowing from base into process adpressed to backs of anthers	Marsdenia

	a	Stems herbaceous to fleshy, erect, prostrate or twining, with well-developed leaves to ± leafless and tuberculate but tubercles not arranged into angles Flowers not fleshy
	b	Stems fleshy, with leaves reduced to minute rudiments or absent, leaf rudiments borne on tubercles arranged into 4 or more angles along stems Flowers fleshy

	a	Corona present only as spreading, somewhat arched ridge behind anthers Style head with slender apex covered by anthers Follicles single by abortion (corolla with slender tube inflated at base)	Orthanthera
	b	Corona present as two series with outer series sometimes much reduced to low ridge between anthers, then usually much taller behind inner lobes (behind anthers) Style head obtuse above Follicles single or paired

	a	Roots hard, somewhat woody and fusiform (not arising from fleshy tuber) Follicles single by abortion
	b	Roots soft, often fleshy and fusiform or arising from swollen tuber Follicles paired

	a	Corolla shortly campanulate to globose-campanulate (with globose to cupular tube), usually densely shaggy-pubescent on inside of lobes Inner corona lobes adpressed to anthers and rarely slightly exceeding them Pollinaria with short thick corpuscle and pollinia longer than broad Plant erect and slender with filiform leaves	Sisyranthus
	b	Corolla deeply lobed and ± rotate (with short bowl-shaped tube), microscopically pubescent on lobes Inner corona lobes rising up in centre and connate above style head Pollinaria with slender corpuscle (longer than broad) and pollinia broader than long Plant ± creeping with ovate- or orbicular-cordate leaves	Anisotoma

	a	Anthers ascending to erect, pressed into sides of style head
	b	Anthers horizontal and pressed into top of style head

	a	Corolla lobes long, slender and reflexed against pedicel, guide rails minute and ± horizontal beneath edge of style head Plant erect and slender with filiform leaves	Macropetalum
	b	Corolla lobes and guide rails not as above Plant erect to climbing, mostly with cordate leaves

	a	Corolla tube often with inflated base, 1-3 times as long as lobes	Riocreuxia
	b	Corolla shallowly bowl-shaped, deeply lobed (tube < 0.5 times length of lobes)	Emplectanthus

	a	Corolla with tube longer than maximum breadth and inner corona lobes exceeding anthers, connivent into column above style head (rarely shorter than anthers)	Ceropegia
	b	Corolla rotate to campanulate, tube broader than long, if longer, then inner corona lobes not exceeding anthers

	a	Flowering stems slender, unbranched, glabrous Leaves ± glabrous and ± reduced to midrib only, filiform and 1-2 mm broad, glabrous Exterior of corolla glabrous	Tenaris
	b	Flowering stems short, usually spreading and branched, often pubescent Leaves pilose, usually with distinct blade narrowing into petiole and to apex Exterior of corolla pilose	Brachystelma

	a	Outer and inner series of corona lobes vertically well separated on staminal tube and not partly or wholly fused to one another (outer corona often disc-like)
	b	Outer and inner series of corona lobes not vertically separated on staminal tube and partly or wholly fused to one another (outer corona never disc-like)

	a	Leaf rudiments with small stipular denticles Corona stipitate, outer series resting on rim or sides of cup formed by annulus	Duvalia
	b	Leaf rudiments without stipular denticles Corona not stipitate, outer series spreading on base of tube and often partly fused to it	Huernia

	a	Tubercles on stems arranged into 6 or more angles
	b	Tubercles on stems arranged into 4 or 5 angles

	a	Each tubercle on stem armed (at least when young) with 1 or more spines (1.5-)3-15 mm long
	b	Each tubercle on stem with a small persistent leaf < 1 mm long or leafless

	a	Spines 3 per tubercle Flowers deeply tubular Outer corona with long slender lobules, each tipped with a tear-like knob	Tavaresia
	b	Spines 1 per tubercle Flowers rotate to shallowly bowl-shaped Lobes of outer corona short, without apical knob

	a	Stem angles > 10 Inner corona lobes without dorsal horn	Hoodia
	b	Stem angles 6-9 Inner corona lobes each with a conspicuous dorsal horn	X Hoodiopsis

	a	Stems with 10 or more angles, each tubercle with small conical leaflet usually sunken into apex	Lavrania
	b	Stems with 6-8 angles Leaflet not distinguishable from tubercle

	a	Inflorescences each with a single flower and a single bract Outer corona forming pectinate ring around gynostegium Pollinia broader than long	Pectinaria
	b	Inflorescences each with several flowers and bracts Outer corona not pectinate Pollinia longer than broad	Notechidnopsis

	a	Stems, pedicels, sepals and outside of corolla pubescent (stems sometimes ± glabrous) Leaves deciduous, erect (spreading in S. engleriana ) Flowers often covered inside with fine slender hairs	Stapelia
	b	Stems, pedicels, sepals and outside of corolla glabrous Leaves spreading or absent

	a	Pollinia relatively large with broad, ± cupular caudicle attached to base of pollinium Insertion crest twisted onto dorsal surface of pollinium
	b	Pollinia small, with small ± circular attachment on ventral surface of pollinium Insertion crest exactly along outer edge of pollinium

	a	Outer corona much reduced to absent (as spreading lobe beneath gynostegial grooves) Deep nectarial cavity present behind outer corona Flowers borne near apices of stems Pollinia ± ellipsoidal	Piaranthus
	b	Outer corona not much reduced Nectarial cavity shallow Flowers borne at any height on stem Pollinia ± D-shaped

	a	Surface of stem micropapillate (dull and not shiny), tubercles obtuse and not tapering into leaf rudiments, stem ± leafless	Tromotriche
	b	Surface of stem smooth (± shiny), tubercles tapering into leaf rudiments, not obtuse or leafless

	a	Leaf rudiments deltoid to subulate, usually with clearly demarkated base, caducous, with small multicellular hairs in stipular position and along margin but lacking stipular denticles Corolla usually covered with multicellular papillae	Tridentea
	b	Tubercles on stem tapering to fine point and leaf rudiment without obvious base, without small hairs in stipular position but usually with stipular denticles Corolla from deeply rugulose to smooth but rarely with multicellular papillae

	a	Stems creeping; inner corona lobes pubescent	Orbeanthus
	b	Stems not creeping; inner corona lobes ± glabrous

	a	Stems not creeping; inner corona lobes ± glabrous	Orbeopsis
	b	Inflorescences few-flowered

	a	Flowers > 30 mm in diameter	Orbea , Pachycymbium lugardii & P. rogersii
	b	Flowers < 30 mm in diameter	Pachycymbium & Orbea paradoxa

	a	Flowers produced towards apex of stem in many small inflorescences
	b	Flowers produced towards base of stem, usually only 1 inflorescence per stem

	a	Stems hard, tubercles tapering into hardened teeth, without differentiated leaf rudiment	Quaqua
	b	Stems soft, tubercles not hardened at tip, bearing small differentiated leaf rudiments	Caralluma

	a	Inner corona laterally flattened, rising above anthers and connate in centre Pollinia longer than broad	Stapeliopsis
	b	Inner corona dorsiventrally flattened, adpressed to backs of anthers and not exceeding them Pollinia broader than long	Ophionella