Family Ixonanthaceae

Ixonanthaceae Planch. ex Klotzsch

~ Simaroubaceae

Excluding Irvingiaceae (= Simaroubaceae p.p.)

Habit and leaf form. Trees, or shrubs; non-laticiferous and without coloured juice. Leaves alternate; spiral, or distichous (then asymmetric); petiolate; non-sheathing; not gland-dotted; simple; epulvinate. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate (the stipules small), or exstipulate. Lamina margins entire, or serrate, or dentate. Leaves without a persistent basal meristem.

Leaf anatomy. Stomata present; paracytic.

Stem anatomy. Secondary thickening developing from a conventional cambial ring. Xylem with fibre tracheids; without libriform fibres. Vessel end-walls simple. Primary medullary rays mixed wide and narrow. Wood parenchyma apotracheal.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite (mostly).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes, or in panicles (thyrses). Inflorescences terminal, or axillary. Flowers small; regular (or nearly so); not resupinate; neither papilionaceous nor pseudo-papilionaceous; usually 5 merous. Free hypanthium absent. Hypogynous disk present; intrastaminal; annular (to cupular, well developed).

Perianth with distinct calyx and corolla; (8–)10; 2 whorled; isomerous. Calyx (4–)5; 1 whorled; polysepalous, or gamosepalous (then connate only basally). Calyx lobes markedly longer than the tube. Calyx regular; imbricate, or contorted. Corolla (4–)5; 1 whorled; polypetalous; imbricate, or contorted; persistent (often, and becoming indurated), or deciduous (?).

Androecium 5–10–20. Androecial members unbranched; free of the perianth (sometimes adnate to the intrastaminal disk); all equal, or markedly unequal; free of one another. Androecium exclusively of fertile stamens. Stamens 5, or 10, or 20; isomerous with the perianth, or diplostemonous, or polystemonous; with the filaments sigmoid-folded in bud; filantherous (the filaments expanded at the base). Anthers not becoming inverted during development; dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate; 2-celled.

Gynoecium 2 carpelled, or (4–)5 carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil 2–10 celled (?). Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2 locular, or (4–)5 locular (sometimes unilocular towards the top, the partitions falling short, and sometimes with secondary false septa). Locules secondarily divided by ‘false septa’, or without ‘false septa’. Gynoecium stylate. Styles 1; apical. Stigmas 1; capitate. Placentation axile to apical. Ovules 1 per locule, or 2 per locule; funicled; pendulous; arillate, or non-arillate; anatropous; bitegmic; crassinucellate (?). Endosperm formation nuclear (?).

Fruit non-fleshy; dehiscent; a capsule; without fleshy investment. Capsules septicidal, or septicidal and loculicidal. Seeds scantily endospermic; with a testa; winged, or wingless.

Physiology, biochemistry. Proanthocyanidins present. Ellagic acid present.

Peculiar feature. Non-mangrove species.

Geography, cytology. Tropical. Pantropical.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Geraniales. Cronquist’s Subclass Rosidae; Linales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Malpighiales.

Species about 30. Genera 4, or 5; Allantospermum(?), Cyrillopsis, Ixonanthes, Ochthocosmus, Phyllocosmus.

A poor description. Satisfactory representation of recent notions on the proper dispositions of several genera previously referred to Simaroubaceae will necessitate thorough overhaul of the descriptions presented in this package (cf. Irvingiaceae, Kirkiaceae, Picramniaceae, Simaroubaceae, Surianaceae, Stylobasiaceae).