Family Bombacaceae

Bombacaceae Kunth

~ Malvaceae (Bayer et al., 1999)

Habit and leaf form. Trees (often having the trunk bulging and specialised for water storage). Leaves deciduous; alternate; spiral; petiolate; non-sheathing; simple, or compound; when compound, palmate. Lamina dissected, or entire; often palmatifid; pinnately veined, or palmately veined. Leaves stipulate. Stipules caducous. Leaves without a persistent basal meristem.

Leaf anatomy. Mucilaginous epidermis commonly present. Hairs present. Complex hairs present; often peltate.

Adaxial hypodermis present (e.g.Durio), or absent. The mesophyll containing mucilage cells (extending from the epidermis), or not containing mucilage cells; with sclerencymatous idioblasts, or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Chorisa).

Stem anatomy. Cork cambium present; initially superficial. The cortex containing cristarque cells, or without cristarque cells. Cortical bundles present (occasionally), or absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones. Xylem with libriform fibres; with vessels. Vessel end-walls simple. Vessels without vestured pits. Tile cells present (Durio and Pterospermum types). Wood partially storied (VPI, VP), or not storied; parenchyma apotracheal and paratracheal (predominantly apotracheal, but vasicentric always present as well).

Reproductive type, pollination. Plants hermaphrodite. Pollination often cheiropterophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence unit cymose. Inflorescences short cymes. Flowers usually large; more or less regular; cyclic, or partially acyclic. Sometimes the androecium acyclic.

Perianth with distinct calyx and corolla, or sepaline (the corolla sometimes absent); 10, or 5 (rarely); 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous (basally); valvate (with glandular hairs at the base). Epicalyx present (often), or absent. Corolla when present (i.e. usually), 5; 1 whorled; contorted.

Androecium 5–100 (i.e. to ‘many’). Androecial members commonly interpretable as branched; when numerous, maturing centrifugally; free of the perianth; coherent (generally), or free of one another; when cohering, 1 adelphous, or 5 adelphous (in 5–15 separate bundles, or the bundles basally connate into a tube). Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present external to the fertile stamens (antesepalous). Stamens 5–100 (usually ‘many’); isomerous with the perianth to polystemonous. Anthers dehiscing via longitudinal slits; introrse; unilocular. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; colpate, or porate, or colporate, or foraminate; usually psilate; 2-celled.

Gynoecium 2–5(–8) carpelled. The pistil 2–5(–8) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2–5(–8) locular. Styles 1. Stigmas dry type; papillate; Group II type. Placentation axile. Ovules 2–6 per locule (?— ‘2 or more’); ascending; arillate (often), or non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral (usually), or persistent. Synergids hooked (sometimes with filiform apparatus). Endosperm formation nuclear. Endosperm haustoria present; chalazal. Embryogeny asterad.

Fruit non-fleshy (usually), or fleshy (rarely); usually dehiscent, or indehiscent (rarely); nearly always a capsule. Capsules loculicidal (usually), or valvular (occasionally). Seeds scantily endospermic, or non-endospermic. Endosperm when present, oily. Cotyledons 2. Embryo chlorophyllous (3/3); often curved.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Not cyanogenic. Alkaloids present (rarely doubtfully), or absent. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (2 genera). Saponins/sapogenins absent. Sugars transported as sucrose (in the four genera sampled). C3. C3 physiology recorded directly in Chorisia. Anatomy non-C4 type (Durio).

Geography, cytology. Sub-tropical to tropical. Widespread, especially America. X = mainly 28, 36 or 40.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Malvales. Cronquist’s Subclass Dilleniidae; Malvales. APG (1998) Eudicot; core Eudicot; Rosid; Eurosid II. APG 3 (2009) Order: Malvales.

Species 180. Genera 30; Adansonia, Aguiaria, Bernoullia, Bombacopsis, Bombax, Catostemma, Cavanillesia, Ceiba, Chorisia, Coelostegia, Cullenia, Durio, Eriotheca, Gyranthera, Huberodendron, Kostermansia, Matisia, Neesia, Neobuchia, Ochroma, Pachira, Patinoa, Phragmotheca, Pseudobombax, Quararibea, Rhodognaphalon, Rhodagnaphalopsis, Scleronema, Septotheca, Spirotheca.

Bayer et al. expand Malvaceae to include Bombacaceae, Sterculiaceae and Tiliaceae, consequent on a combined analysis of plastid atpB and rbcL DNA sequences.

Economic uses, etc. ‘Durian’ is the fruit of Durio zebethinus; Ceiba fruit supplies kapok; very light wood (balsa, corkwood) from Ochroma.

Illustrations.
• Technical details: Bombax.

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