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). Plants non-succulent. 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. Leaves without a persistent basal meristem. Domatia occurring in the family (Ailanthus); manifested as hair tufts.
Leaf anatomy. 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), or paracytic (e.g. Castela). Hairs present; eglandular, or glandular.
Adaxial hypodermis present (occasionally), or absent. Lamina dorsiventral (except Harrisonia); without secretory cavities (except Harrisonia). The mesophyll with spherical etherial oil cells, or without etherial oil cells; with sclerencymatous idioblasts (very commonly), or without sclerenchymatous idioblasts (?); usually containing calcium oxalate crystals. The mesophyll crystals druses, or solitary-prismatic. Minor leaf veins without phloem transfer cells (Ailanthus, Quassia).
Stem anatomy. Cork cambium present; initially superficial. The cortex containing cristarque cells, or without cristarque cells. Nodes tri-lacunar, or multilacunar (7). Secondary thickening developing from a conventional cambial ring. Xylem with tracheids, or without tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres; with vessels. Vessel end-walls simple (mostly), or simple and reticulately perforated. Vessels without vestured pits. Wood storied, or partially storied; parenchyma apotracheal, or paratracheal (very variable, abundant to scarce or absent).
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 unit 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, biochemistry. Not cyanogenic. Polyacetylenes recorded, or not found. Alkaloids present, or absent. Iridoids not detected. Arthroquinones detected (Brucea); polyacetate derived. Proanthocyanidins absent. Flavonols present, or absent; kaempferol and quercetin. Ellagic acid present (Alanthus, Quassia), or absent (Ailanthus). Arbutin absent. Saponins/sapogenins absent. Aluminium accumulation not found. Sugars transported as sucrose (in Simarouba). C3. C3 physiology recorded directly in Ailanthus.
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, Perrierodendron, Picrolemma, Pleiokirkia, Quassia, Samadera, Simaba, Simarouba, Soulamea.
Note that 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.
• Technical details: Quassia, Ailanthus.
• Technical details: Quassia (Lindley).