Annonaceae Juss. Gen. Pl.: 283, 1789 (as "Anoneae "Anoneae") nom. cons.
Description.
Trees, scrambling shrubs or lianas, up to 50 m tall, monoecious, dioecious or putatively androdioecious. Indumentum, when present, of simple, fasciculate, stellate, or scale-like hairs. Leaves alternate, simple, distichous, margins entire, stipules absent. Inflorescences terminal or axillary, ramiflorous in leaf axils, on young or old leafless branches or cauliflorous, single to many-flowered, pedunculate or subsessile, bracts often present. Flowers bisexual or unisexual, actinomorphic, generally trimerous. Sepals in a single whorl, (2)3(4), valvate or imbricate in bud, free or basally to fully connate. Petals 3, 4 or 6, in 1 or 2(3) whorls, generally differentiated into an inner and outer whorl alternating with the sepals, valvate or imbricate in bud, free, basally or fully connate. Stamens 3 to numerous, inserted onto a flat or convex receptacle; anthers generally exceeded by the connective apex, which forms a a protective cover at the top of the stamen; connective apex flat, extended (tongue shaped) or absent; filaments short or absent, free or rarely fused; staminodes absent or present. Carpels 1 to numerous, free or more rarely fused (syncarpous) in flower; stigma capitate, oblong or variously folded; ovules 1 to numerous, uni- or biseriate, basal or lateral. Fruit generally apocarpous, each carpel producing a single monocarp, or more rarely pseudosyncarpous (carpels fusing during fructification) or syncarpous (unilocular fruits resulting from syncarpous flowers), indehiscent or sometimes dehiscent; monocarps 1 to numerous, sessile to long-stipitate, cylindrical, globose, ovoid, ellipsoid, club-shaped or moniliform, 3 to over 40 mm in length, usually large; seeds 1 to numerous per monocarp, uni- or biseriate, or unordered in syncarpous species, sometimes with arilor sarcotesta; endosperm ruminate, hard.
Distribution.
Pantropical, from the Pacific and northern Australia to South East Asia (including southern China), India, Madagascar, tropical Africa, temperate eastern North America south to Central America and South America. 113 genera, and around 2550 species.
In Cameroon, 28 genera and 163 species reported to date.
Notes.
Several Annonaceae species have been introduced and are commonly cultivated across the country. Monoon longifolium (Sonn.) B.Xue & R.M.K.Saunders (= Polyalthia longifolia (Sonn.) Hook.f. & Thomson) is sold and grown as an ornamental, and planted mainly along roads in major towns and gardens. Cananga odorata (Lam.) Hook.f. & Thomson (ylang ylang) is sold and planted as an ornamental, with its large flowers emitting a strong sweet scent especially at night. Several non-native species of Annona are planted in gardens for their large sweet fruits, especially A. muricata L. Annona glabra L. is naturalized in coastal mangrove regions of West Africa including Cameroon. These non-native species are not treated here.
Key to the genera of Annonaceae in Cameroon
| 1 | Midrib of leaf blade clearly raised above | 2 |
| - | Midrib of leaf blade sunken,impressed, or flat above | 4 |
| 2 | Petals fused at base (even just shortly); fruits in a single unit (syncarpous) | 3 |
| - | Petals free; fruits in several independent monocarps (apocarpous) | Polyceratocarpus pellegrinii |
| 3 | Corolla lobes similar and equal in length, forming a distinct tube at the base, margins generally flat | Isolona |
| - | Corolla lobes clearly differentiated into inner and outer petals; the outer ones longer than inner ones, margins generally undulate or crisped | Monodora |
| 4 | Liana or scrambling shrub | 5 |
| - | Tree or shrub | 14 |
| 5 | Hook-shaped structures (modified inflorescence) present on branches even in juvenile plants | Artabotrys |
| - | Hook-shaped structures absent | 6 |
| 6 | Indumentum of stellate and/or fasciculate hairs | Uvaria (pro parte) |
| - | Indumentum (if present) of simple hairs | 7 |
| 7 | Anthers septate (few species) | 8 |
| - | Anthers not septate (most species) | 9 |
| 8 | Petals subequal; stipe shorter than seeded section of monocarp; indehiscent; several seeds per monocarp | Xylopia thomsonii |
| - | Outer petals longer than inner; stipe at least twice as long as seeded section of monocarp; monocarps indehiscent; seed 1 per monocarp | Neostenanthera myristicifolia |
| 9 | Leaves bicolored; above green, below glaucous to whitish; monocarps moniliform when more than one seed, ovules uniseriate | 10 |
| - | Leaves green on both sides; monocarps not moniliform, globose to conical, ovules biseriate | 12 |
| 10 | Tertiary venation percurrent when viewed from below, or if venation obscure, then stamens <35 | Monanthotaxis |
| - | Tertiary venation reticulate and stamens> 40 | 11 |
| 11 | Inflorescences terminal (leaf opposed or extra-axillary) | Afroguatteria |
| - | Inflorescences axillary | Sphaerocoryne |
| 12 | Receptacle columnar or elongated; petals 6 to 12 in 2 or 3 whorls | Toussaintia |
| - | Receptacle convex but not columnar; petals 6 in two whorls | 13 |
| 13 | Sepals entirely fused, enclosing flower in bud, tearing as flower enlarges; fruits pseudosyncarpous | Letestudoxa |
| - | Sepals free or basally fused, not enclosing flower in bud; fruits apocarpous | Uvaria (pro parte) |
| 14 | Indumentum of scale-like hairs (easily visible with a hand lens) | Meiocarpidium |
| - | Indumentum (if present) of stellate, fasciculate or simple hairs | 15 |
| 15 | Indumentum of stellate and/or fasciculate hairs and fruits pseudosyncarpous | Duguetia |
| - | Indumentum of simple hairs, or glabrous; fruits mostly apocarpous (pseudosyncarpous in Annona and Anonidium) | 16 |
| 16 | Sepals 2; petals 4 | Uvariopsis |
| - | Sepals 3; petals 3 or 6 | 17 |
| 17 | Inner bark/slash yellow; petals 3, opposite the 3 sepals | Annickia |
| - | Inner bark/slash cream to reddish; petals 6, or if 3 then only 2 sepals present | 18 |
| 18 | Petals fused into a clear tube at the base, plicate (transversely folded) in bud | Hexalobus |
| - | Petals free, petals not plicate (not folded in bud) | 19 |
| 19 | Outer petals reduced, sepal like, smaller than inner petals | 20 |
| - | Outer petals not reduced, subequal to or larger than inner petals | 21 |
| 20 | Secondary veins 11 to 17 pairs; inflorescence compact, generally up to than 10(-15) mm long | Brieya |
| - | Secondary veins (15-)22 to 66 pairs; inflorescence compact to lax, but always longer than 16 mm | Piptostigma |
| 21 | Receptacle cylindrical; anther connective reduced to a tuft of hairs | Mischogyne |
| - | Receptacle convex to flat; connective well developed, discoid to apiculate | 22 |
| 22 | Tertiary venation percurrent | 23 |
| - | Tertiary venation reticulate | 25 |
| 23 | Leaf apex obtuse, rounded or emarginate (in Cameroonian species); fruits (pseudo)syncarpous | Annona |
| - | Leaf apex acute, acuminate or caudate; fruits apocarpous | 24 |
| 24 | Outer petals much longer than inner petals; inner petals forming a dome over the receptacle; anthers septate; seed 1 per monocarp | Neostenanthera |
| - | Petals sub equal or outer slightly longer; inner petals not forming a dome over the receptacle; anthers not septate; seeds> 1 per monocarp | Polyceratocarpus (pro parte) |
| 25 | Sepals reduplicate-valvate, buds ridged | Uvariastrum |
| - | Sepals not reduplicate-valvate, buds not ridged | 26 |
| 26 | Petals homogenously red to pink, all reflexed at maturity; anthers bright yellow in vivo at maturity; carpel 1; monocarp 1 | Sirdavidia |
| - | Petals green, yellow, cream, not reflexed or only curved outward; anthers not bright yellow; carpels> 1; monocarps generally more than one | 27 |
| 28 | Anthers septate; monocarps dehiscent | Xylopia |
| - | Anthers not septate; monocarps not dehiscent | 29 |
| 29 | Individuals androdioecious or dioecious with separate male, female or bisexual flowers | 30 |
| - | Individuals with bisexual flowers | 31 |
| 30 | Flowering peduncles present,> 50 mm long; stamens more than 30; fruits (pseudo)syncarpous | Anonidium |
| - | Flowering peduncle absent; stamens less than 30; fruits apocarpous | Greenwayodendron |
| 31 | Flowering pedicels> 15 mm; sepals free; outer petals up to five times longer than inner petals | Cleistopholis |
| - | Flowering pedicels <15 mm; sepals basally fused; petals subequal | 32 |
| 32 | Petioles 2-5 mm long, 1-2 mm wide; petals 3(4), less than 10 mm long, basally fused | Dennettia |
| - | Petioles> 4 mm long, 3-9 mm wide; petals 6, 10 mm or longer, free | Uvariodendron |
Synoptic key
Genera in parentheses means some but not all species have the indicated trait.
Liana or scrambling to scandent shrub: Afroguatteria; Artabotrys; Uvaria; ( Monodora); Monanthotaxis; ( Neostenanthera); Sphaerocoryne; Toussaintia; Letestudoxa; ( Xylopia).
Tree: Annickia; Annona; Anonidium; Brieya; Cleistopholis; Duguetia; Greenwayodendron; Hexalobus; Isolona; Meiocarpidium; Mischogyne; Monodora; Neostenanthera; Piptostigma; Polyceratocarpus; Uvariastrum; Uvariodendron; Uvariopsis; Xylopia .
Slash of the bark yellow: Annickia .
Stilt roots or buttresses present: ( Xylopia).
Indumentum of stellate hairs: Annickia, Duguetia; Uvaria .
Indumentum of lepidote hairs: Meiocarpidium .
Hook-like structures on branches: Artabotrys .
Leaves discolorous, light green to whitish below: Afroguatteria; Cleistopholis, Monanthotaxis; Piptostigma, Sphaerocoryne; ( Uvaria), ( Xylopia).
Trunk whitish overall: Cleistopholis; Greenwayodendron .
Leaves with many parallel secondary veins (> 25): ( Piptostigma), ( Uvaria), ( Uvariodendron).
Midrib clearly raised above: Isolona; Monodora; ( Polyceratocarpus).
Sepals 2; petals 4: Uvariopsis; ( Monanthotaxis).
Sepals reduplicate-valvate (margins folded in bud): Uvariastrum, Toussaintia .
Petals fused into a single whorl with a distinct tube: Hexalobus; Isolona .
Petals 3: Annickia; Dennettia; ( Monanthotaxis).
Petals 9 to 10 inserted in 2 to 3 whorls: Toussaintia .
Petals plicate in bud, transversely folded when open: Hexalobus .
Inner petals much longer than outer: Brieya; Piptostigma .
Anthers septate: Neostenanthera; Xylopia .
Staminodes present: ( Monanthotaxis); Xylopia .
Androdioecious, dioecious or monoecious: Anonidium; Greenwayodendron; ( Monanthotaxis); Polyceratocarpus; Uvariopsis .
Pseudosyncarpous fruits (individual monocarps visible): Annona, Anonidium, Duguetia, Letestudoxa .
Fruits syncarpous (individuals monocarps not visible) with numerous unordered seeds: Isolona; Monodora .
Monocarps moniliform: Monanthotaxis; ( Xylopia).
Monocarps dehiscent: Xylopia .
Seeds arillate: ( Duguetia); ( Xylopia).
Seeds with a sarcotesta: ( Xylopia).