Family Ptaeroxylaceae

Ptaeroxylaceae Sonder

~ Sapindaceae, Rutaceae

Habit and leaf form. Trees; bearing essential oils, or without essential oils (?); resinous, or not resinous (?). Leaves usually deciduous; alternate (Bottegoa, Cedrelopsis), or opposite (Ptaeroxylon); when alternate, spiral; petiolate; not gland-dotted; aromatic; compound; pinnate (pari- or (im)paripinnate, in Cedrelopsis and Ptaeroxylon, the leaflets opposite or alternate, oblique), or bipinnate (biparipinnate, Bottegoa). Lamina pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins (of the leaflets) entire.

Leaf anatomy. Extra-floral nectaries present (on the leaves of Bottegoa and Ptaeroxylon), or absent (Cedrelopsis). Abaxial epidermis papillose, or not papillose. Mucilaginous epidermis absent. Stomata present; anomocytic (Bottegoa, Ptaeroxylon), or cyclocytic (Cedrelopsis).

Adaxial hypodermis absent. Lamina dorsiventral (Ptaeroxylon), or isobilateral (Cedrelopsis), or dorsiventral to isobilateral (Bottegoa); without secretory cavities. The mesophyll with spherical etherial oil cells; without calcium oxalate crystals.

Stem anatomy. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with libriform fibres (non-septate). Vessel end-walls horizontal to oblique; simple. Vessels without vestured pits. Primary medullary rays narrow. Wood parenchyma scanty paratracheal, or apotracheal (scarce).

Reproductive type, pollination. Unisexual flowers present. Plants polygamomonoecious, or dioecious.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes. The ultimate inflorescence unit cymose. Inflorescences axillary; small axillary cymes or false racemes. Flowers small; regular; 4 merous, or 5 merous; cyclic. Floral receptacle developing a gynophore (this slight, associated with the disk). Free hypanthium absent. Hypogynous disk present; intrastaminal.

Perianth with distinct calyx and corolla; 8, or 10; 2 whorled; isomerous. Calyx 4, or 5; 1 whorled; shortly gamosepalous; blunt-lobed, or toothed; regular; more or less imbricate. Corolla 4, or 5; 1 whorled; polypetalous; imbricate, or valvate.

Androecium 4, or 5. Androecial members free of the perianth; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5; isomerous with the perianth; oppositisepalous; filantherous (the filaments not basally flattened). Filaments not appendiculate (scaleless). Pollen shed as single grains. Pollen grains aperturate; 3–4 aperturate; colporate.

Gynoecium 2 carpelled (Bottegoa, Ptaeroxylon), or 3–5 carpelled (Cedrelopsis). Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 2–5 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary 2–5 locular; subsessile, or stipitate (?). Gynoecium stylate. Styles 2–5; (shortly) partially joined. Stigmas 2–5; capitate. Ovules 1 per locule, or (1–)2(–3) per locule (Cedrelopsis); pendulous; apotropous; with dorsal raphe; non-arillate; campylotropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle.

Fruit non-fleshy; indehiscent (Bottegoa), or a schizocarp. Mericarps of schizocarps, 2–5; comprising follicles and samaroid (samaroid, dehiscing via the inner suture). Fruit of Bottegoa, a samara (surrounded by a thin, broad wing). Seeds endospermic (the endosperm thin and fleshy), or non-endospermic; winged (above), or wingless (Bottegoa). Embryo curved, or bent. The radicle lateral.

Geography, cytology. Paleotropical and Cape. Tropical. Tropical and Southern Africa, Madagascar.

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 (as a synonym of Rutaceae).

Species 4, or 5. Genera 3, or 4; Cedrelopsis, Ptaeroxylon, Bottegoa, (?)Kirkia.

Leroy 1959, Ptaeroxylaceae, in Compt. Rend. Acad. Sci. Paris 248, 1001–1003; Leroy 1960, Ptaeroxylaceae, in Journ. Agr. Trop. Bot. Appl. 7, 455–456; White and Styles 1966, Ptaeroxylaceae, in Flora Zambesiaca 2, 547–550; Van der Ham et al. 1995, Bottegoa in Kew Bull. 50, 243–265.