Apocynaceae Juss.

Apocynaceae, H. Huber. Flora of West Tropical Africa 2. 1963

Morphology General Habit

Trees, shrubs or climbers, rarely perennial herbs, with latex

Morphology Leaves

Leaves opposite or verticillate, rarely alternate, simple, entire; stipules usually absent

Morphology Reproductive morphology Flowers

Flowers hermaphrodite, actinomorphic

Morphology Reproductive morphology Flowers Calyx

Calyx often glandular inside; lobes 5 or rarely 4, imbricate

Morphology Reproductive morphology Flowers Corolla

Corolla tubular, variously shaped; lobes contorted-imbricate, very rarely valvate

Morphology Reproductive morphology Flowers Androecium

Stamens 5 or rarely 4, inserted in the tube; filaments free or rarely united; anthers often sagittate, free or connivent around the stigma, rarely adherent to the latter, 2-celled, opening lengthwise, connective often produced at the apex; pollen granular; disk usually present, annular, cupular or of separate glands

Morphology Reproductive morphology Flowers Gynoecium

Style 1, split at the base or entire, thickened and stigmatose below the apex; ovules 2 or more in each carpel Ovary superior, 1-celled with 2 parietal placentas or 2-celled with the placentas adnate to the septa, or carpels 2 and free or connate only at the base with ventral placentas in each carpel

Morphology Reproductive morphology Fruits

Fruit entire and indehiscent or of 2 separate carpels, baccate, drupaceous or follicular

Morphology Reproductive morphology Seeds

Seeds mostly with endosperm and large straight embryo, often winged or appendaged with long silky hairs

Timothy Utteridge & Gemma Bramley (2020). The Kew Tropical Plant Families Identification Handbook, Second Edition. Kew Publishing Royal Botanic Gardens, Kew

Note

Climbers or trees. Sap or exudate present, usually white. Stipules absent. Leaves opposite, entire, often with regular secondary veins. Flowers bisexual with tubular corollas; ovary superior. Fruit often a pair of woody follicles.

Recognition

Characters of similar families: Rubiaceae: sap lacking, leaves with interpetiolar stipules ovary inferior. Myrtaceae: leaves with pellucid gland dots, flowers usually with many anthers, ovary inferior. Clusiaceae: sap usually yellow, leaves often with pellucid dots or lines. Loganiaceae: sap lacking, style not swollen. Oleaceae: sap lacking, leaves often sub-opposite, stamens 2.

Morphology General Habit

Lianas or climbers, more rarely trees, shrubs, or herbs

Morphology General Sap

Sap or exudate almost always present, white (rarely colourless, yellow or red)

Morphology Leaves Stipules

Stipules absent (mostly)

Morphology Leaves

Leaves opposite, usually decussate or whorled (rarely alternate); simple; lamina margins entire

Morphology Reproductive morphology Inflorescences

Inflorescence cymose, racemose or flowers solitary

Morphology Reproductive morphology Flowers

Flowers often large and showy; actinomorphic, bisexual; sepals 5 free; corolla tubular, with 5 lobes, usually convolute in bud; stamens 5, inserted on the corolla tube and alternating with the corolla lobes, forming a cone around the expanded stylar head (compare with Asclepiadoideae with modified anthers and pollen transfer structures); disk present or absent; ovary superior (rarely semi-inferior), 2(–8) fused carpels, or 2 free carpels united by the style; 1–2 locular with 1–many ovules in each locule; style simple with a swollen apex

Morphology Reproductive morphology Fruits

Fruit a berry or drupe, or often a pair of dehiscent follicles

Morphology Reproductive morphology Seeds

Seeds with endosperm; mostly with a coma of hairs at one or both ends; coma absent from berries and drupes.

Distribution

A large cosmopolitan family traditionally split into the woody Apocynaceae and herbaceous Asclepiadaceae. In this book, we treat Asclepiadoideae as the most derived subfamily of an enlarged Apocynaceae, the whole family totalling c. 375 genera and ± 5,500 species.

Description Author

David Goyder

Timothy M. A. Utteridge and Laura V. S. Jennings (2022). Trees of New Guinea. Kew Publishing. Royal Botanic Gardens, Kew

Distribution

A large family of about 415 genera and 4500 species, occurring worldwide in the tropics and subtropics and in warm temperate regions.

Recognition

The family can be recognised by the presence of white latex from cut surfaces, the usually opposite leaves with pinnate venation, the tubular corolla with lobes overlapping and twisting to the left or right, the superior ovary and the fruits which are often paired.

Morphology General Habit

Climbers, shrubs and trees, rarely herbs. Latex present, usually white, sometimes cream or yellow

Morphology Leaves

Leaves opposite, simple, petiolate, opposite or whorled, usually coriaceous, colleters (awl-shaped glands) frequently present in the axils, venation pinnate

Morphology Leaves Stipules

Stipules absent

Morphology Reproductive morphology Inflorescences

Inflorescences terminal or axillary, cymose, corymbose, occasionally paniculate or fasciculate

Morphology Reproductive morphology Flowers

Flowers bisexual, actinomorphic, 5-merous (rarely 4-merous), often fragrant; calyx lobes free or fused into a tube; corolla tubular, erect or spreading apically, lobes overlapping and twisted to the left or to the right; stamens usually 5, inserted inside corolla tube, filaments usually very short, anthers dorsifixed, ovate or sagittate; disk present or absent, if present then an annular ring or 2- or 5-lobed; ovary superior, rarely semi-superior, apocarpous with 2 carpels united by a common style or syncarpous and bilocular or unilocular

Morphology Reproductive morphology Fruits

Fruit a berry, drupe, follicle or capsule, solitary or paired

Morphology Reproductive morphology Seeds

Seeds simple, arillate, winged or with a coma.

Apocynaceae, E.A. Omino. Flora of Tropical East Africa. 2002

Morphology General Habit

Trees, shrubs, lianas, or sometimes herbs (not in our area, except introduced ones); latex nearly always present, usually white, sometimes clear, yellow or red

Morphology Leaves

Leaves simple, opposite, whorled, or less often alternate (as in Adenium), pinnately veined, entire, rarely stipulate

Morphology Reproductive morphology Flowers

Flowers bisexual, mostly actinomorphic, 5- or rarely 4-merous, fragrant

Morphology Reproductive morphology Flowers Calyx

Calyx often with colleters inside, free or united at the base, imbricate in bud

Morphology Reproductive morphology Flowers Corolla

Corolla tubular, contorted or occasionally valvate, free, overlapping to the right or left in bud, sometimes with a corona

Morphology Reproductive morphology Flowers Androecium

Stamens included or exserted, epipetalous, free or connate to the style; filaments often very short, epipetalous; anthers frequently triangular, of two cells longitudinally dehiscent, often partly sterile, sometimes with apical appendages

Morphology Reproductive morphology Flowers Gynoecium

Ovary superior or sometimes partly inferior, 1-celled and with 2 parietal placentas, 2-celled and with an axile placenta in each cell or composed of 2, or more, separate or at the base partly united carpels each with an adaxial placenta; ovules 2 to many; style one, often split at the base when carpels more or less separate; pistil head composed of a large variously shaped stigmatic basal part and a stigmoid apex; disk annular, cupular, composed of separate glands, or absent

Morphology Reproductive morphology Fruits

Fruit entire or consisting of two (rarely more) separate or partly united carpels, baccate, drupaceous, or follicular

Morphology Reproductive morphology Seeds

Seeds in dry fruits often winged or with a coma, mostly with an endosperm and a large embryo

Note

The corona presents many diagnostic characters for generic and specific recognition. Following the system devised by Liede & Kunze in Pl. Syst. Evol. 185: 275–284 (1993), it may be corolline (derived from the corolla) or gynostegial (from the staminal column). Corolline coronas can be divided into those occuring in the corolla lobe sinuses and those forming an annulus in the corolla tube. Gynostegial coronas again have two basic elements, a staminal corona attached dorsally to the stamens, and an interstaminal corona, and these elements can be combined in a number of ways: e.g. staminal corona lobes only; a fused ring of staminal and interstaminal lobes; fused staminal and interstaminal corona with additional staminal lobes. Notes on floral structures within the more derived subfamilies of Apocynaceae: the five stamens are fused apically to the expanded stylar head and together form a compound structure called the gynostegium. The ovary is therefore almost entirely concealed within a ring of stamens (the staminal column) whose filaments are usually fused into a tube, but free in subfamily Periplocoideae. Only the sterile apex of the stylar head remains visible, level with or extending beyond the anthers; the receptive parts of the stylar head are on its underside behind the frequently sclerified margins of the anthers which form a chamber for the deposition of pollen. The pollen transfer apparatus is formed by secretions from the stylar head and, in periplocoid genera, generally consists of a spatulate translator onto which pollen tetrads, or more rarely pollen masses (pollinia), from adjacent anthers are shed; in the two remaining subfamilies, the secretions form a central corpusculum linked by caudicles or translator arms to 2 or 4 pollinia of adjacent anthers – the unit is transferred in its entirity from one flower to another and is called a pollinarium.

Gemma Bramley, Anna Trias-Blasi & Richard Wilford (2023). The Kew Temperate Plant Families Identification Handbook. Kew Publishing Royal Botanic Gardens, Kew

Recognition

Characters of similar families: Rubiaceae: no sap or exudate, leaves with interpetiolar stipules, ovary inferior. Gentianaceae: no sap or exudate, leaves sometimes 3- or 5-nerved at base, fruit a capsule, rarely a berry. Myrtaceae: leaves with pellucid gland dots, flowers usually with many anthers, ovary inferior. Oleaceae: no sap or exudate, leaves often sub-opposite, flowers usually 4-merous, stamens 2. Convolvulaceae: leaves alternate, corolla with mid-petaline bands, fruit usually a capsule.

Morphology General Habit

Climbers or lianas, perennial herbs, trees or shrubs, more rarely subshrubs or succulents

Morphology General Sap

Sap or exudate almost always present, usually white

Morphology Leaves Stipules

Stipules absent (mostly)

Morphology Leaves

Leaves simple, opposite usually decussate or whorled (rarely alternate); lamina margins entire

Morphology Reproductive morphology Inflorescences

Inflorescence cymose, racemose or flowers solitary

Morphology Reproductive morphology Flowers

Flowers actinomorphic, bisexual; sepals 5, free; corolla tubular, with 5 lobes, usually convolute in bud; stamens 5, inserted on the corolla tube and alternating with the corolla lobes; or corolla mostly valvate in bud, stamens 5, fused to the expanded stylar head to form a compound structure, the gynostegium; corona lobes often present on gynostegium, occasionally on corolla, or on both; pollen grouped into waxy pollinia, linked by corpusculum secreted from stylar head and distributed in pairs (pollinaria); disk present or absent; ovary superior (rarely semiinferior), 2(–8) fused carpels, or 2 free carpels united by the style; 1–2 locular with 1–many ovules in each locule; style simple with a swollen apex

Morphology Reproductive morphology Fruits

Fruit usually 1–2 dehiscent follicles but also a berry, drupe or capsule

Morphology Reproductive morphology Seeds

Seeds with endosperm; mostly with a coma of hairs at one or both ends; coma absent from berries and drupes.

Distribution

A large cosmopolitan family of 366 genera and ca. 6,450 species, most diverse in the tropics.

Note

Flowers bisexual; corolla with a well-developed or short tube; stamens and style head closely associated or fused; ovary superior.

Description Author

Nina Davies

Goyder, D. J., Gilbert, M. G. & Venter, H. J. T. (2020). Apocynaceae (part 2). In: M. A. García (ed.), Flora Zambesiaca, Vol. 7(3). Royal Botanic Gardens, Kew.

Morphology Reproductive morphology Flowers Androecium Stamens

The five stamens are fused apically to the expanded stylar head and together form a compound structure called the gynostegium Stamens epipetalous from base to near mouth of corolla tube, alternating with corolla lobes, glabrous or hairy; filaments free or fused to coronal feet and/or laterally to interstaminalnectaries; anthers free, inner bases fused to style-head forming a gynostegium, laterotrorse; pollen in rhomboidal, decussate or linear tetrads or in pollinia, shed onto translators

Morphology Reproductive morphology Flowers Gynoecium Ovary

The ovary is therefore almost entirely concealed within a ring of stamens (the staminal column) whose filaments are usually fused into a tube, but free in subfam Periplocoideae Ovaries 2, free, semi-inferior, styles 2, apically fused into style-head; style-head pentangular, ovoid, deltoid or rarely cylindrical-ovoid, bearing translators on upper surface in between adjacent anthers

Morphology Reproductive morphology Flowers Gynoecium Style

Only the sterile apex of the stylar head remains visible, level with or extending beyond the anthers; the receptive portions of the stylar head are on its underside behind the frequently sclerified margins of the anthers which form a chamber for the deposition of pollen

Morphology Reproductive morphology Flowers Pollen

The pollen transfer apparatus is formed by secretions from the stylar head and, in periplocoid genera, generally consists of a spathulate translator onto which pollen tetrads, or more rarely pollen masses (pollinia), from adjacent anthers are shed; in the two remaining subfamilies, the secretions form a central corpusculum linked by caudicles or translator arms to 2 or 4 pollinia of adjacent anthers – the unit is transferred in its entirity from one flower to another and is called a pollinarium.

Morphology Reproductive morphology Flowers Corona

The corona presents many diagnostic characters for generic and specific recognition. Following the system devised by Liede & Kunze in Pl. Syst. Evol. 185: 275–284 (1993), it may be corolline (derived from the corolla) or gynostegial (from the staminal column) Corolline coronas can be divided into those occurring in the corolla lobe sinuses and those forming an annulus in the corolla tube Corona corolline, alternating with petals, 1 or 2-whorled; lower whorl mostly present, inserted on inner wall of corolla tube, always above stamen whorl, of 5 lobes, lobes simple or segmented, free or fused, mostly basally fused with staminal filaments forming coronal feet, coronal feet sometimes also fused to interstaminalnectaries forming a coronal annulus; upper whorl, when present, arising from corolla lobe sinuses, pocket-like or pocket-lobular with lobe from rim of pocket

Morphology Reproductive morphology Flowers Gynostegium

Gynostegial coronas again have two basic elements, a staminal corona attached dorsally to the stamens, and an interstaminal corona, and these elements can be combined in a number of ways: e.g. staminal corona lobes only; a fused ring of staminal and interstaminal lobes; fused staminal and interstaminal corona with additional staminal lobes. Gynostegium concealed in corolla tube or exposed from it

Morphology Roots

Roots often tuberous

Morphology Reproductive morphology Inflorescences

Inflorescences terminal and/or axillary, simple cymose or paniculate cymose, few- to many-flowered

Morphology Reproductive morphology Flowers Receptacle

Translator of receptacle (spoon), stalk (present or absent) and basal sticky disc (viscidium)

Distribution

Thirty-three genera and approximately 190 species occur in Africa, Madagascar, Asia, South-east Asia and Australia. Of the 18 genera found in Africa, 16 are endemic to the continent. Approximately 100 species are endemic. Nine genera and 44 species are present in the Flora Zambesiaca area.

Morphology General Habit

Trees, shrubs, lianas, or sometimes herbs, mostly with white sticky latex Perennial climbers, shrubs or herbaceous geophytes with white or occasionally red or orange latex

Morphology Leaves

Leaves opposite, whorled, or less often alternate, simple, pinnately veined, entire Leaves opposite, rarely alternate, whorled or fascicled, petiolate to sessile, axils with dentate and/or hairy colleters; blades simple, venation pinnate, often with colleters on main veins, margin entire

Morphology Leaves Stipules

Stipules usually absent Interpetiolar stipules of simple lines, dentate colleterate ridges or a collar of frills

Morphology Reproductive morphology Flowers

Flowers bisexual, mostly actinomorphic, 5- or rarely 4-merous Flowers actinomorphic, pentamerous, semi-epigynous, variously coloured, glabrous or hairy, sometimes aromatic. Sepals free, often with paired colleters at inner bases

Morphology Reproductive morphology Flowers Calyx

Calyx often with colleters inside

Morphology Reproductive morphology Flowers Corolla

Corolla tubular, sometimes with a corona; lobes contorted or occasionally (not in FZ area) valvate Petals fused, tube saucer-shaped, campanulate, cylindrical or reflexed

Morphology Reproductive morphology Flowers Androecium

Stamens inserted on the corolla; filaments free from each other or exceptionally (not in FZ area) united in a tube, often very short, frequently continued downwards as ridges at the corolla inside; anthers frequently triangular, connivent over and often coherent with the stigma, 2-celled, often partly sterile, sometimes with apical appendages; cells parallel, discrete, dehiscent throughout by a longitudinal slit Pollen granular

Morphology Reproductive morphology Flowers Gynoecium

Ovary superior or sometimes partly inferior, 1-celled and with 2 parietal placentas, 2-celled and with an axile placenta in each cell, or composed of 2, rarely more, separate or at the base partly united carpels each with an adaxial placenta; ovules 2 to many; style one, often split at the base when carpels more or less separate; stigma composed of a large variously shaped part, usually called the clavuncula, with laterally and/or basally the receptive zone, which is — if stigma coherent with the anthers — below the level of coherence, and a small apical usually sterile (also in FZ) so-called stigma

Morphology Reproductive morphology Flowers Nectaries

Disk annular, cupular, composed of separate glands, or absent Nectaries epipetalous at base of tube, opposite corolla lobes, interstaminal, surrounding upper half of ovary, lobular or pocket-like, free or fused with coronal feet

Morphology Reproductive morphology Fruits

Fruit entire or consisting of two, rarely more, separate or partly united carpels, baccate, drupaceous, or follicular

Morphology Reproductive morphology Seeds

Seeds in dry fruits often winged or with a coma, mostly with endosperm and a large embryo Seeds compressed, mostly obliquely ovate, with coma or collar (rarely) of hairs. Follicles paired or single

Milliken, W., Klitgard, B. and Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://creativecommons.org/licenses/by/3.0

Morphology General Habit

Large shrubs (Calotropis, introduced in New World), lianas, vines, herbs or subshrubs, mostly perennial, often sending up annual shoots from a perennial rootstock, occasionally annual, and rarely strongly succulent (introduced in the Americas); latex usually white, but clear in non-native, succulent Ceropegieae

Morphology Leaves

Leaves simple, entire, most commonly opposite but occasionally whorled, or reduced to a scale or spine (in introduced succulent genera)

Morphology Reproductive morphology Flowers

Flowers actinomorphic, bisexual, 5- merous except for the paired carpels; corolla fused at least at the base, varying from rotate or shallowly campanulate to tubular or funnel-shaped, lobes twisted in bud and overlapping to the right, or valvate; coronal structures often present either on corolla (infrequently) or more commonly on gynostegium (formed from fusion of stamens and stylar head; stamens inserted at base of corolla, filaments fused into a tube, anthers with specialised marginal wings or guide rails; pollen aggregated into pollinia (one per locule, two per pollinarium), these bound by a waxy outer wall, pollinia attached to hard, brown or black, grooved corpusculum by translator arms, forming a pollinarium extracted from the flower as a unit; ovary superior, apocarpous with two carpels, these fused apically to form a stylar head with stigmatic surfaces on underside (secretions from the stylar head are formed into five discrete clip-like structures (corpuscula) which assist in pollen transport)

Morphology Reproductive morphology Fruits

Fruits paired dehiscent follicles (frequently single by abortion)

Morphology Reproductive morphology Seeds

Seeds generally flattened, ovate, mostly with a narrow marginal rim and a tuft of hairs at one end.

Distribution

Throughout, but most diverse in seasonally dry habitats. All native except those highlighted in list above [Stapelia, Calotropis, Gomphocarpus]. Most endemic to the New World, but Marsdenia is pan-tropical, and Asclepias is most diverse in North America and Africa, with just 12 species extending into central and South America.

Note

Number of genera: c. 50 genera native to neotropics (largest genera listed first in each group, then alphabetical) Marsdenieae Marsdenia R.Br. Ceropegieae [Stapelia L., and possibly other genera - introduced] Asclepiadeae: Asclepiadinae Asclepias L. [Calotropis R.Br., Gomphocarpus R.Br. - introduced] Asclepiadeae: Cynanchineae Cynanchum L. [note only c. 12 New World species belong here - most NW 'Cynanchum' are now referable to genera in the Metastelmatinae or Orthosiinae] Asclepiadeae: MOG unplaced Pentacyphus Schltr. [2 species - high Andean] Diplolepis R.Br. [temperate S America] Tassadia Decne. Asclepiadeae: Gonolobinae (NW endemic subtribe) Gonolobus Michx. Matelea Aubl. Dictyanthus Decne. Fischeria DC. Gyrostelma E.Fourn. Hypolobus E.Fourn. Labidostelma Schltr. Macroscepis Kunth Metalepis Griseb. Pherotrichis Decne. Polystemma Decne. Prosthediscus Donn. Sm. Rojasia Malme Schubertia Mart. Stelmagonum Baill. Asclepiadeae: Metastelmatinae (NW endemic subtribe) Ditassa R.Br. Metastelma R.Br. Ampelamus Raf. Barjonia Decne. Blepharodon Decne. Cyathostelma E.Fourn. Gonioanthela Malme Hemipogon Decne. Macroditassa Malme Minaria T.U.P.Konno & Rapini Nautonia Decne. Nephradenia Decne. Peplonia Decne. Petalostelma E.Fourn. Rhyssostelma Decne. Asclepiadeae: Orthosiinae (NW endemic subtribe) Jobinia E.Fourn. Orthosia Decne. Asclepiadeae: Oxypetalinae (NW endemic subtribe) Oxypetalum R.Br. Philibertia Kunth Funastrum E.Fourn. Araujia Brot. Kerbera E.Fourn. Morrenia Lindl. Schistogyne Hook. & Arn. Stenomeria Turcz. Tweedia Hook. & Arn. Widgrenia Malme The Asclepiadoideae is the most derived of five subfamilies now included within an expanded Apocynaceae. Its extreme floral modifications, with complicated pollination syndromes and structures, often with corona elements in one or more whorls, and with pollen aggregated into pollinaria, led earlier workers to classify it as a separate family; but in reality the trend towards the complicated flowers of the Asclepiadoideae starts midway through Apocynaceae s.s., where the stylar head abutts closely underneath the cone of anthers, forming a functional gynostegium. From there on, progressive synorganisation of floral organs, accompanied by a shortening of the corolla tube, lead to greater control over pollen transfer, through the Apocynoideae and the Old-World subfamilies Periplocoideae and Secamonoideae, to the highly derived Asclepiadoideae. The basal subfamily Rauvolfioideae is much more variable both vegetatively and florally than these more derived groups.

Diagnostic

If the plant is a stem-succulent with leaves reduced to scales, you are looking at an introduced Stapelia or allied genus in the Ceropegieae. The pollinaria will be held erect, and have a translucent germination zone. If the pollinia are held erect, i.e. above the position of the corpusculum, and do not possess a translucent germination zone, then the tribe is Marsdenieae. Marsdenia is the only representative of this tribe in the New World - clue: if the anthers extend significantly beyond the position of the corpusculum, there will be space for the pollinia to be held erect. Marsdenia tends also to have a tubular corolla obscuring the gynostegium, and five erect staminal corona lobes. NB. Barjonia (Asclepiadeae) may have erect pollinia, but will never have a tubular corolla obscuring the gynostegium. If the pollinia are pendant or horizontal relative to the position of the corpusculum, then the plant is in tribe Asclepiadeae - the vast majority of New-World asclepiads, and all the remaining NW genera. Asclepias can be recognised easily by the combination of erect herb or subshrub AND a staminal corona formed of five concave fleshy organs with a tooth arising from the cavity of each lobe. Corolla and corona are often brightly coloured. Now look at the pentagonal drum of stamens - the 'head' of the gynostegium. If this is flattened and subdiscoid, with very short anther wings relative to the diameter of the disc, the pollinia will be displaced laterally in relation to the corpusculum, and you are looking at Gonolobinae - the two big genera being Matelea and Gonolobus (see below for diagnostic features). Of the remaining groups, the pollinaria of Oxypetalinae are generally large, and structurally complex, sometimes with teeth on the flattened translator arms. Flowers also tend to be large, and generally the stylar head extends beyond the staminal column as a well-developed appendage. Genera of the Metastelmatinae and remaining unplaced groupings tend to have minute or small flowers. Other striking floral characters include a corona of one or more whorls. This can be derived from the corolla, or from the gynostegium, usually the stamens, but is occasionally absent. Key differences from similar families: Subfamilies Apocynoideae and Rauvolfioideae (Apocynaceae in the narrow sense) lack the pollinarium - pollen is generally distributed as tetrads rather than pollinia. If a corona is present, then it is found only on the corolla. The stylar head and the cone of anthers are positioned part way up the corolla tube rather than at the base, and do not form a compound structure, the gynostegium. Fruit morphology is much more varied, particularly in the basal Rauvolfioideae, where seeds lack a coma of hairs, and the fruit is often an indehiscentberry. Asclepias - erect herbs or subshrubs; flowers generally brightly coloured, red, yellow or white, corona of 5 lobes on the back of the stamens, concave with a prominent tooth arising from the cavity of the lobe; follicles always single by abortion. Stapelia - stem-succulent with large, foul-smelling, reddish or brownish flowers attracting flies (native to Africa). Gonolobus - slender twiners; flowers rotate with exposed discoidhead to gynostegium and laterally disposed pollinia, anthers with dorsal appendages; flowers commonly green; follicles with longitudinal wings. Matelea - erect herbs or more usually slender twiners; flowers rotate with exposed discoidhead to the gynostegium and laterally dispose pollinia, anthers laking dorsal appendages; flowers often smelly, green or reddish brown and fly-pollinated; follicles lacking longitudinal wings, but often with soft spiny processes. Cynanchum - twiners; corona tubular, at least at the base, around the gynostegium. Marsdenia - fairly robust twiners, often with large, thickish leaves, some species associated with inselbergs; corolla usually with well-developed tubular portion enclosing the gynostegium, corona of 5, generally fleshyerect lobes on back of stamens; pollinia erect. Schubertia - twiner with large, urceolate white flowers. Metastelma - twiners with small flowers; corolla lobes generally pubescent above, corona of 5 staminal lobes. Ditassa - mostly twiners with small flowers; corolla lobes mostly not obviously pubescent, corona of five 'double' lobes - each lobe has a ligule on the inner face. Minaria - ericoid shubshrubs with flowers similar to Ditassa (recently split from Ditassa). Funastrum - mostly vigorous, free-flowering twiners often with their feet in seasonally flooded pools; stems semisucculent and photosynthetic (leaves often drop off); umbels of white or cream flowers, corona mosly with a tubular outer ring, and 5 fleshy lobes on the back of the anthers. Oxypetalum - erect herbs or twiners; flowers moderate in size; mostly with conspicuous stylar head appendages (divided into 2 or more lobes); corona lobes arising from the corolla tube NOT on the back of the anthers; pollinaria large, and often with teeth on the translator arms; distribution centred on Brazil. Philibertia - Andean version of Oxypetalum but with corona on back of stamens not on the corolla, or absent; stylar head appendages variable or absent. Distinguishing characters (always present): Subfamily Asclepiadoideae can be characterised by the presence of a gynostegium in which the expanded stylar head is fused to the androecium by cell fusion, and where the narrow gap between the sclerified wings of adjacent anthers form five grooves. The form of the pollinarium is also diagnostic for the subfamily, and indeed tribes within it can be determined by close observation of pollinarium structure (see below). Pollen of one antherlocule is aggregated into a pollinium encased by a waxy wall. This pollen mass is linked to another in an adjacent anther by a pair of translator arms and a single corpusculum. So two pollinia linked by translator arms to a single corpusculum form a pollinarium that can be extracted from the flower as a single unit. The corpusculum is usually black or dark brown, and sits at the top of the groove between adjacent anthers.

Asclepiadaceae, A.A. Bullock. Flora of West Tropical Africa 2. 1963

Morphology General Habit

Twining or erect shrubs or perennial herbs; leaves opposite, linear to orbicular-obovate, entire, or rarely lobed or toothed

Morphology Reproductive morphology Inflorescences

Inflorescence cymose, most frequently umbelliform but sometimes with flowers more or less racemosely fasciculate along a simple or branched rhachis

Morphology Reproductive morphology Flowers

Flowers regular, pentamerous; calyx-tube very short or obsolete; corolla contorted, imbricate or valvate, gamopetalous, the lobes sometimes connivent at the apex; filaments united into a tube, anthers connivent throughout their length and united with the expanded style apex, introrse, bilocular and provided with lateral horny wings

Morphology Reproductive morphology Flowers Corona

Corona arising from the staminal column, very variable in form or rarely absent or reduced to five small fleshy tubercles

Morphology Reproductive morphology Flowers Androecium

Pollen in waxy masses (pollinia) attached in pairs by caudicles of various form to 5 corpuscular usually horny sutured pollen carriers arising from the style apex and concealing the stigmatic surfaces

Morphology Reproductive morphology Flowers Gynoecium

Ovary of two separate carpels; styles free to the apex where they are united in a peltate disk which is convex, conical or beaked; ovules multiseriate, on a single adaxial placenta in each carpel

Morphology Reproductive morphology Fruits

Fruit of two (by abortion often one) erect or divergent follicles which may be linear to ovoid or ellipsoidal, membranous to woody, smooth or winged or variously armed with soft or indurated prickles, always dehiscent lengthwise adaxially

Morphology Reproductive morphology Seeds

Seeds compressed, often with a membranous or thickened margin and nearly always crowned with a coma of silky hairs

Timothy Utteridge & Gemma Bramley (2020). The Kew Tropical Plant Families Identification Handbook, Second Edition. Kew Publishing Royal Botanic Gardens, Kew

Note

Herbs, shrubs or twiners. Sap or exudate white or clear. Leaves opposite, entire; stipules absent. Corolla united; style and stamens fused to form gynostegium; pollen distributed as pollinaria. Fruit mostly of paired follicles.

Recognition

Characters of similar families: Apocynaceae (sensu stricto): gynostegium absent, pollen granular, corona absent or on corolla only. Rubiaceae: sap lacking, leaves with interpetiolar stipules, ovary inferior. Clusiaceae: sap usually yellow, leaves often with pellucid dots or lines. Loganiaceae: sap lacking, style not swollen. Oleaceae: sap lacking, leaves often sub-opposite, stamens 2.

Morphology General Habit

Perennial herbaceous or succulent herbs, shrubs, twiners or lianas, very rarely annuals or ephemerals

Morphology General Sap

Sap or exudate present, white or clear

Morphology Leaves Stipules

Stipules absent

Morphology Leaves

Leaves opposite, decussate or whorled; simple; lamina margins entire

Morphology Reproductive morphology Inflorescences

Inflorescence cymose, racemose or flowers solitary

Morphology Reproductive morphology Flowers

Flowers bisexual, actinomorphic; sepals 5 free; corolla with very short to well-developed tube, 5 lobes, mostly valvate in bud; stamens 5, fused to the expanded stylar head to form a compound structure, the gynostegium; corona lobes of diverse form often present on gynostegium, occasionally on corolla, or on both; pollen grouped into waxy pollinia, linked by corpusculum secreted from stylar head and distributed in pairs (pollinaria); ovary superior, 2 free carpels united by the style, with 1–many ovules in each locule; style simple with an expanded stylar head

Morphology Reproductive morphology Fruits

Fruit a pair of dehiscent follicles, frequently single by abortion

Morphology Reproductive morphology Seeds

Seeds with endosperm; mostly with a coma of hairs at one end.

Distribution

The largest and most derived of 5 subfamilies of Apocynaceae. Most diverse in seasonally dry tropics and subtropics, but with some temperate genera. c. 170 genera and 3,000 species.

Description Author

David Goyder

George R. Proctor (2012). Flora of the Cayman Isands (Second Edition). Royal Botanic Gardens, Kew

Morphology General Habit

Mostly perennial herbs, erect, scandent or twining, or sometimes woody shrubs (rarely arborescent), usually with milky sap; leaves opposite or rarely whorled; stipules poorly developed or lacking. Inflorescence a usually umbel-like or raceme-like axillary cyme; flowers of very complicated structure, perfect, regular; calyx with very short or no tube, the 5 lobes imbricate or open in bud; corolla 5-lobed, the lobes twisted or valvate; usually a corona present, this simple or consisting of 5 or more scales or lobes, adnate to the corolla-tube or to the staminal column, highly varied in structure

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 5, inserted at or near the base of the corolla, the filaments flat, short, and usually joined to form a tube, united with the stigma to form a ‘gynostegium’; anthers 2-celled, opening inwardly, often extended at the base and tipped with a membranous appendage; pollen aggregated in waxy or granular masses called ‘pollinia’, these usually solitary in each anther-cell, and agglutinated with the stigma by 5 glandular ‘corpuscles’ which extrude the pollinia after dehiscence of the anthers

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary superior, of 2 distinct carpels, surrounded by the stamen- tube; styles 2, distinct below the stigma; stigma 1, peltately dilated and forming a more or less pentagonal disc; ovules numerous in each carpel, pendulous and overlapping on the placentas.

Morphology Reproductive morphology Fruits

Fruit of 2 follicles, or often only 1 developing; seeds numerous, compressed, and usually bearing a tuft of long soft white silky hairs; endosperm thin and cartilaginous; embryo large, with flat cotyledons.

Distribution

A family of perhaps 130 genera and 2,000 species, widely distributed in temperate and tropical regions.

Note

Except perhaps for the orchids, the flowers of Asclepiadaceae are the most highly specialised of any group of plants.

Periplocaceae, A.A. Bullock. Flora of West Tropical Africa 2. 1963

Morphology General Habit

Climbing, twining or erect, softly woody or occasionally with wiry stems, or herbaceous perennials with a tuberous rootstock; leaves opposite, entire, linear to very broad, pinnately nerved; stipules absent, but sometimes with a stipular frill around the stem at the nodes which may become woody; inflorescence a terminal cyme often lateral by sympodial growth of the axis, sometimes racemiform or umbelliform; bracts very small; flowers bisexual, sometimes functionally unisexual and then dioecious; calyx-tube very short or obsolescent, segments 5, valvate or imbricate but opening very early; corolla gamopetalous, 5-lobed, tube short or sometimes as long as or longer than the lobes, lobes contorted or very rarely valvate; corona of 5 lobes arising from the base of the stamen filaments, of varied form, or rarely absent or reduced to tubercles; stamens 5, inserted in the corolla-tube or at its throat, free from each other, but with the anthers pressed together and to the expanded apex of the style; anthers basifixed, introrse, usually with a scarious apical appendage inflexed over the style; pollen granular, in tetrads discharged on to 5 spathulate pollen carriers derived from the expanded part of the style and with a glandular base; pollen carriers concealing the 5 stigmatic surfaces; carpels two, joined only by their styles, which unite to form a flat or variously elongated head; ovules numerous, multiseriate on a single adaxial placenta; fruit of two (or one by abortion or pollination failure) divergent or reflexed sessile follicles; follicles more or less fusiform and often greatly elongated, or sometimes broadly ovoid, smooth, glabrous or hairy, sometimes warted or winged, finally dehiscing lengthwise adaxially; seeds flat, often winged, and crowned with a coma of soft silky hairs; endosperm present; embryo straight, almost as long as the seed, cotyledons flat

Use

Apocynaceae are often poisonous with some genera used for their medicinal properties and as poisons. Species of Amsonia, Asclepias, Mandevilla, Nerium, Plumeria, Stephanotis and Vinca are used as ornamentals.