The Families of Angiosperms

L. Watson and M.J. Dallwitz

Icacinaceae Miers

Alternatively Irvingbaileyaceae.

Including Emmotaceae Van Tiegh., Iodaceae Van Tiegh., Leptaulaceae Van Tiegh., Metteniusaceae p.p., Phytocreneae (Phytocrenaceae) R.Br., Pleurisanthaceae Van Tiegh., Sarcostigmataceae Van Tiegh.; excluding Pennantiaceae J.G. Agardh, Stemoneuraceae

Habit and leaf form. Trees, ‘arborescent’, shrubs, and lianas; laticiferous, or non-laticiferous, without coloured juice. Plants green and photosynthesizing. Self supporting, or climbing; tendril climbers (the lianes), or scrambling. Helophytic, or mesophytic. Leaves alternate (nearly always), or opposite (somtimes, in climbers); spiral; more or less leathery, or membranous (rarely); petiolate (the petioles canaliculate); non-sheathing; not gland-dotted; simple. Lamina dissected (sometimes being palmately 5–7 lobed), or entire (usually); pinnately veined (mostly), or palmately veined; cross-venulate. Leaves exstipulate. Lamina margins entire to dentate; slightly revolute, or flat. Leaf development not ‘graminaceous’. Domatia occurring in the family (known from 4 genera); manifested as pits, or pockets (when present).

Leaf anatomy. Hydathodes present (occasionally), or absent. Mucilaginous epidermis present, or absent. Stomata anomocytic, or anisocytic, or paracytic. Hairs of assorted unicellular and multicellular forms present. Urticating hairs present (e.g., in Phytocrene), or absent. Lamina with secretory cavities, or without secretory cavities. Secretory cavities when present, containing latex. The mesophyll with sclerenchymatous idioblasts, or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Cassinopsis).

Axial (stem, wood) anatomy. The cortex containing cristarque cells, or without cristarque cells. Secretory cavities present, or absent; when present, with latex. Cork cambium present; initially superficial. Nodes variously unilacunar, or tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles, or comprising a ring of bundles, or comprising two or more rings of bundles, or consisting of scattered bundles (?); collateral, or bicollateral (recorded in medullary bundles of Iodes). Internal phloem present, or absent. Medullary bundles present, or absent. Secondary thickening developing from a conventional cambial ring, or anomalous (see illustration). The anomalous secondary thickening when present, via concentric cambia, or from a single cambial ring.

The wood diffuse porous. The vessels very small to medium; solitary, or radially paired, or in radial multiples, or clustered, or in tangential arcs (in various combinations). The vessel end-walls scalariform (then usually mostly solitary), or simple, or scalariform and simple. The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids, or without tracheids; without vasicentric tracheids; with fibre tracheids (especially in forms with scalariform perforation plates), or without fibre tracheids; with libriform fibres, or without libriform fibres; without septate fibres. The fibres without spiral thickening. ‘Included’ phloem present (from a single cambial ring, e.g. in lianoids of the tribe Sarcostigmateae), or absent. The wood not storied.

Reproductive type, pollination. Unisexual flowers present, or absent. Plants hermaphrodite (usually), or andromonoecious, or gynomonoecious, or dioecious (especially the lianas), or androdioecious, or gynodioecious, or polygamomonoecious (‘rarely polygamous to dioecious’).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (the pedicels articulated); in cymes, or in racemes (usually), or in spikes, or in panicles. The ultimate inflorescence units cymose, or racemose (usually). Inflorescences terminal, or axillary (usually), or leaf-opposed, or epiphyllous (Leptaulus), or cauliflorous. Flowers bracteate (usually), or ebracteate; small; odourless; regular, or somewhat irregular to very irregular (rarely); neither papilionaceous nor pseudo-papilionaceous; (3–)4–5(–7) merous (but mostly pentamerous); cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent (usually), or present; when present, extrastaminal, or intrastaminal.

Perianth with distinct calyx and corolla (usually), or sepaline (rarely apetalous), or petaline (K absent in Pyrenacantha); (3–)4–5(–6), or (6–)8–10(–12); 1 whorled, or 2 whorled (usually); isomerous. Calyx when present (i.e. usually), (3–)4–5(–6); 1 whorled; usually glabrous, gamosepalous (usually shalloly cupular), or polysepalous (rarely); lobulate, or blunt-lobed, or toothed; regular; usually fleshy; non-accrescent; imbricate (usually), or valvate (rarely). Corolla when present (i.e. usually), (3–)4–6(–7); 1 whorled; polypetalous (usually), or gamopetalous (rarely); usually valvate; regular.

Androecium (3–)4–5(–6). Androecial members free of the perianth, or adnate (to the corolla tube); all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens (3–)4–5(–6); isomerous with the perianth; oppositisepalous; alternating with the corolla members; laminar, or filantherous (the filaments filiform, or fleshy, or broad and flattened). Anthers dorsifixed, or basifixed; dehiscing via longitudinal slits; introrse (usually), or extrorse, or latrorse; appendaged (from the connective), or unappendaged. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer to initially with more than one middle layer (these ephemeral). Tapetum glandular. Pollen grains aperturate, or nonaperturate (Stachyanthus); when aperturate, mostly 3(–7) aperturate; colpate, or porate, or colporate, or foraminate; 3-celled (in Miquelia and Phytocrene).

Gynoecium (2–)3(–5) carpelled. The pistil 1 celled (usually), or 3–5 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 1 locular (usually, by abortion), or 3–5 locular (rarely). Gynoecium stylate (usually shortly). Styles 1; attenuate from the ovary; apical. Stigmas (2–)3(–5). Placentation usually apical; when plurilocular (i.e. rarely) axile, or apical. Ovules in the single cavity usually 2 (back to back — rarely only one); when plurilocular (i.e. rarely) 1–2 per locule; pendulous; arillate (with a funicular thickening near the micropyle), or non-arillate; anatropous; unitegmic; crassinucellate (e.g., Icacina, Iodes, Pyrenacantha), or tenuinucellate (Phytocrene). Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral, or persistent. Synergids hooked (with filiform apparatus). Endosperm formation nuclear. Endosperm haustoria present, or absent; when present, chalazal (Nothapodites).

Fruit fleshy, or non-fleshy; indehiscent; a drupe (usually, in globose clusters in Phytocrene, with a fleshy lateral appendage in Apodytes), or a samara (sometimes?). The drupes with one stone. Fruit 1 seeded. Seeds endospermic. Endosperm oily. Cotyledons 2. Embryo chlorophyllous (1/1); straight to curved.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. Cyanogenic. Alkaloids present, or absent. Verbascosides detected (Cassinopsis). Iridoids detected; ‘Route I’ type (normal and seco). Saponins/sapogenins present, or absent. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present, or absent; quercetin. Ellagic acid absent (genera). Aluminium accumulation demonstrated.

Geography, cytology. Sub-tropical to tropical. Pantropical, plus South Africa and Eastern Australia. X = 10, 11.

Taxonomy. Subclass Dicotyledonae; at least mostly Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Celastrales. APG III core angiosperms; core eudicot; Superorder Asteranae; lamiid. APG IV Order Icacinales.

Species about 350. Genera 52; Alsodeiopsis, Apodytes, Calatola, Casimirella, Cassinopsis, Citronella, Chlamydocarya, Dendrobangia, Desmostachys, Emmotum, Gonocaryum, Hosiea, Icacina, Iodes, Lavigeria, Leretia, Mappia, Mappianthus, Merrilliodendron, Miquelia, Natsiatopsis, Natsiatum, Nothapodytes, Oecopetalum, Ottoschulzia, Phytocrene, Pittosporopsis, Platea, Pleurisanthes, Polycephalium, Polyporandra, Poraqueiba, Pseudobotrys, Pyrenacantha, Rhaphiostylis, Rhyticaryum, Sarcostigma, Stachyanthus.

General remarks. This family exemplifies the well known difficulties in distributing certain Dicot families between Dahlgren’s Araliiflorae and Corniflorae. It had proved equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli, although the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993). In any case, this 2018 draft compilation requires critical reappraisal consequent on segregation of Metteniusaceae and Stemonuraceae (q.v.), especially re 'esoteric characters' - anatomy, embryology, phytochemistry.

Economic uses, etc. A few cultivated ornamentals (Citronella (Villaresia).

Illustrations. • Apodytes dimidiata: Thonner. • Apodytes dimidiata and Mappia tomentosa: Lindley. • Alsodeiopsis mannii: Hook. Ic. Pl. 11 (1867–71). • Cassinopsis chapelieri: Fl. de Madagascar et Comores 119 (1952). • Citronella mucronata (as Villaresia): Bot. Mag. 137 (1911). • Hosiea sinensis (as Natsiatum): Hook. Ic. Pl. 19 (1889). • Icacina mannii: Bot. Mag. 102 (1876). • Iodes globulifera and I. nectarifera: Fl. de Madagascar et Comores 119 (1952). • Lavigeria macrocarpa, as Icacina: Hook. Ic. Pl. 24 (1894). • Merrilliodendron megacarpum, as ?Stemonurus: Hook. Ic. Pl. 24 (1895). • Nothapodytes pittosporoides, as Mappia: Hook. Ic. Pl. 18 (1888). • Pittosporopsis kerrii: Hook. Ic. Pl. 30 (1911). • Rhaphiostylis ferruginea: Engler & Drude, Die Vegetation der Erde 9 (1910). • Leaf hairs of Platea excelsa and Goniocaryum pyriforme, with one from Cansjera (Opiliaceae). Solereder, 1908. • TS stem of Phytocrene macrophylla, with anomalous secondary thickening (Solereder, 1908).