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The families of flowering plants

L. Watson and M.J. Dallwitz

Simaroubaceae DC.

Including Ailanthaceae J.G. Agardh, Castelaceae J.G. Agardh, Holacanthaceae Jadin, Simabaceae Horan. (p.p.), Soulameae (Soulameaceae) Endl.; excluding Irvingiaceae, Ixonanthaceae, Kirkiaceae, Leitneriaceae, Picramniaceae, Surianaceae.

Habit and leaf form. Trees and shrubs (producing characteristic triterpenoid lactones (simaroubalides), without resin canals, often with very bitter bark, wood and seeds); non-laticiferous. Mesophytic. Leaves alternate; spiral; petiolate; non-sheathing; not gland-dotted; simple (rarely, e.g. Quassia), or compound (usually); pinnate (usually), or unifoliolate, or ternate. Lamina pinnately veined; cross-venulate. Leaves exstipulate (excluding genera referable elsewhere, notably Irvingiaceae and Surianaceae). Lamina margins entire. Leaf development not ‘graminaceous’. Domatia occurring in the family (Ailanthus); manifested as hair tufts.

Leaf anatomy. The leaf lamina dorsiventral (mostly), or bifacial to centric (Harrisonia), or centric (e.g., in Ailanthus, Castela). Extra-floral nectaries present (commonly, on various parts of the leaves), or absent. Abaxial epidermis papillose, or not papillose. Mucilaginous epidermis present, or absent. Stomata present; anomocytic (usually, see illustration), or paracytic (e.g. Castela). Hairs present (of assorted kinds, but mostly simple or uniseriate and sclerenchymatous); eglandular, or glandular. Adaxial hypodermis present (occasionally), or absent. Lamina without secretory cavities (except Harrisonia). The mesophyll with spherical etherial oil cells, or without etherial oil cells; with sclerenchymatous idioblasts (very commonly), or without sclerenchymatous idioblasts (?); usually containing crystals. The crystals druses, or solitary-prismatic. Minor leaf veins without phloem transfer cells (Ailanthus, Quassia).

Axial (stem, wood) anatomy. The cortex containing cristarque cells, or without cristarque cells. Secretory cavities present (in the pith). Cork cambium present; initially superficial. Nodes tri-lacunar, or multilacunar (7). Primary vascular tissues in a cylinder, without separate bundles; collateral. Secondary thickening developing from a conventional cambial ring.

The wood ring porous to diffuse porous. The vessel end-walls simple (mostly), or simple and reticulately perforated. The vessels without vestured pits; without spiral thickening. The axial xylem with tracheids, or without tracheids; with vasicentric tracheids (often), or without vasicentric tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; at least sometimes including septate fibres, or without septate fibres (?). The fibres without spiral thickening. The parenchyma apotracheal, or paratracheal (very variable, abundant to scarce or absent); wood storied, or partially storied.

Reproductive type, pollination. Unisexual flowers present. Plants monoecious, or dioecious, or polygamomonoecious. Gynoecium of male flowers pistillodial, or vestigial, or absent.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually, often numerous), or solitary; in cymes, or in racemes, or in spikes, or in panicles, or in catkins. The ultimate inflorescence units cymose, or racemose. Inflorescences axillary; compound panicles, spikes, racemes or thyrses. Flowers minute, or small; regular; 3–5(–8) merous; cyclic; when hermaphrodite, pentacyclic. Floral receptacle developing an androphore, or developing a gynophore, or with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present (usually), or absent; when present, extrastaminal.

Perianth with distinct calyx and corolla (usually), or sepaline (corolla rarely absent); 6–10(–16); 2 whorled, or 1 whorled (rarely); isomerous. Calyx 3–5(–8); 1 whorled; gamosepalous (usually basally connate), or polysepalous; regular; imbricate (usually), or valvate. Corolla 3–5(–8); 1 whorled; polypetalous; imbricate (usually), or contorted, or valvate; regular.

Androecium (3–)10(–16). Androecial members free of the perianth; free of one another; 2 whorled (usually), or 1 whorled (e.g. Brucea). Androecium exclusively of fertile stamens. Stamens (3–)10(–16); diplostemonous (usually), or isomerous with the perianth (sometimes), or triplostemonous to polystemonous (Quassia); oppositisepalous (usually), or alternisepalous (rarely, e.g. Picrolemma). Filaments appendiculate (often with scales at the base, cf. Rutaceae), or not appendiculate. Anthers dorsifixed (usually), or basifixed (Soulamea, and more or less ventrifixed in Ailanthus); versatile; dehiscing via longitudinal slits; introrse (usually), or extrorse to latrorse (Ailanthus, Soulamea); tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate, or T-shaped (rarely). Anther wall initially with more than one middle layer (2 or 3). Pollen grains aperturate; 3 aperturate; colporate (or colporoidate); 2-celled (in 5 genera).

Gynoecium 1 carpelled (Amaroria), or 2–5(–8) carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil when other than (pseudo-)monomerous, 1 celled, or 2–5(–8) celled. Gynoecium monomerous, or apocarpous to syncarpous; of one carpel (Amaroria), or eu-apocarpous to semicarpous, or synstylous (i.e. carpels weakly united, often free below and united only by the style or stigma); superior. Carpel (when monomerous or apocarpous) apically stigmatic, or with a lateral style, or with a gynobasic style; (when free) 1 ovuled. Ovary if more or less syncarpous, 2–5(–8) locular. Gynoecium stylate. Styles 2–5(–8); free, or partially joined; lateral, or ‘gynobasic’. Stigmas dry type; non-papillate; Group II type. Placentation axile. Ovules 1 per locule; pendulous; epitropous (the micropyle superior); with ventral raphe; hemianatropous to anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped (sometimes with filiform apparatus). Hypostase present. Endosperm formation nuclear. Endosperm haustoria present; chalazal. Embryogeny onagrad.

Fruit fleshy, or non-fleshy; an aggregate, or not an aggregate. The fruiting carpel indehiscent; drupaceous, or baccate, or samaroid. Fruit when syncarpous indehiscent, or a schizocarp. Mericarps when schizocarpic, 2–5; comprising berrylets, or comprising drupelets, or comprising nutlets, or comprising nutlets and comprising drupelets. Fruit when syncarpous capsular-indehiscent, or a berry, or a drupe, or a samara. Seeds more or less non-endospermic. Cotyledons 2 (large, expanded). Embryo chlorophyllous (3/3); straight, or curved.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Ailanthus. Sugars transported as sucrose (in Simarouba). Not cyanogenic. Polyacetylenes recorded, or not found. Alkaloids present, or absent. Anthraquinones detected (Brucea); polyacetate derived. Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols present, or absent; kaempferol and quercetin. Ellagic acid present (Alanthus, Quassia), or absent (Ailanthus). Aluminium accumulation not found.

Geography, cytology. Sub-tropical to tropical. Pantropical and subtropical, to Japan and central Argentina. X = 8, 13(+).

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Rutales. Cronquist’s Subclass Rosidae; Sapindales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Sapindales.

Species about 50. Genera about 20; Ailanthus, Amaroria, Brucea, Castela, Eurycoma, Gymnostemon, Hannoa, Harrisonia (or Rutaceae?), Iridosma, Laumoniera, Perriera, Pierreodendron, Picrolemma, Pleiokirkia, Quassia, Samadera, Simaba, Simarouba, Soulamea.

General remarks. Satisfactory representation of recent notions on the proper dispositions of genera long associated with Simaroubaceae will necessitate thorough overhaul of the descriptions presented in this package (cf. Irvingiaceae, Kirkiaceae, Picramniaceae, Surianaceae, Stylobasiaceae). Adequate comparative data are either unavailable or inaccessible.

Illustrations. • Technical details: Quassia, Ailanthus. • Technical details: Quassia (Lindley). • Quassia schweinfurthii, as Hannoa: Hook. Ic. Pl. 13 (1877–79). • Quassia indica (as Samadera): R. Wight (1840). • Samadera baileyana: Hook. Ic. Pl. 25 (1896). • Simaba monophylla, as Simar(o)uba: Hook. Ic. Pl. 14 (1880–82). • Abaxial leaf epidermis of Rigiostachys (= Recchia) bracteata and axial hairs of Eurycoma longifolia, with leaf hairs of Picramnia coccinea (Picramniaceae); Solereder, 1908.


We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.


Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 12th September 2017. delta-intkey.com/angio’.

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