| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Bombacaceae Kunth

~ Malvaceae-Bombacoideae.

Habit and leaf form. Trees (some attaining enormous size, others short but having wide, bulging trunks that are 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. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral (usually), or bifacial. Mucilaginous epidermis commonly present. Stomata mainly confined to one surface (the lower). Hairs present (usually), or absent. Complex hairs usually present; often peltate, or stellate (cf. Malvaceae). Adaxial hypodermis present (e.g.Durio), or absent. The mesophyll containing mucilage cells (extending from the epidermis), or not containing mucilage cells; with sclerenchymatous idioblasts, or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Chorisa).

Axial (stem, wood) anatomy. Young stems with solid internodes, or with spongy internodes. The cortex containing cristarque cells, or without cristarque cells. Pith sometimes of thin-walled spongy tissue, sometimes of thick-walled, pitted cells. Secretory cavities present (commonly), or absent; when present, with mucilage (and/or with mucilage cells). Cork cambium present; initially superficial. Primary vascular tissues in a cylinder, without separate bundles, or comprising a ring of bundles (when interrupted by broad rays); collateral. Internal phloem absent. Cortical bundles present (occasionally), or absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring.

The wood ring porous to diffuse porous. The vessels medium to large (typically), or small; solitary (mosty), or solitary, radially paired, in radial multiples, clustered, and in tangential arcs. The vessel end-walls simple. The vessels without vestured pits; without spiral thickening. The axial xylem with libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal and paratracheal (predominantly apotracheal, but vasicentric always present as well). The secondary phloem usually more or less stratified into hard (fibrous) and soft (parenchymatous) zones. ‘Included’ phloem absent. Tile cells present (Durio and Pterospermum types). The wood partially storied (VPI, VP), or not storied.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Pollination often chiropterophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes. The ultimate inflorescence units cymose. Inflorescences short cymes. Flowers usually large; more or less regular; cyclic, or partially acyclic. Sometimes the androecium acyclic. Floral receptacle developing an androphore, or with neither androphore nor gynophore.

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. Micropyle not zigzag.

Seedling. Germination phanerocotylar, or cryptocotylar.

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

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 III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Malvales (as a synonym of Malvaceae).

Species 180. Genera 30; Adansonia, Aguiaria, Bernoullia, Bombacopsis, Bombax, Camptostemon, 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.

General remarks. Bayer et al. (1999) expanded Malvaceae to include Bombacaceae, Sterculiaceae and Tiliaceae consequent on a combined analysis of plastid atpB and rbcL DNA sequences. In terms of the descriptions compiled for this package, Bombacaceae differ from Malvaceae sensu stricto (q.v.) in having cheiropterophilous flowers with androecial members free of the perianth, in anther development (wall initially with more than one middle layer and tapetum glandular), psilate pollen, and the eu-syncarpous gynoecium.

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

Illustrations. • Bombax malabaricum (~ B. ceiba): R. Wight (1840). • Bernoullia flammea: Hook. Ic. Pl. 12 (1876). • Camptostemon schultzii: Hook. Ic. Pl. 12 (1876). • Catostemma fragrans: Hook. Ic. Pl. 20 (1891). • Durio zibethinus: König, Trans. Linn. Soc. London 7 (1804). • Durio zibethinus, fruit: König, Trans. Linn. Soc. London 7 (1804). • Eriotheca parvifolia, as Bombax parviflorum: Martius, Nova Gen. et Spec. Pl. Brasiliensium (1824). • Pachira alba: Bot. Mag. 76 (1850). • Pachira aquatica: Ann. Miss. Bot. Gard. 51 (1964). • Pachira sessilis (as Bombacopsis): Ann. Miss. Bot. Gard. 51 (1964). • Pseudobombax septenatum: Ann. Miss. Bot. Gard. 51 (1964). • Rhodagnaphalon lukayense, as Bombax: Thonner. • Leaf hairs of Durio, with Althaea, Malachra and Malvastrum (Malvaceae): 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: 8th June 2026. delta-intkey.com’.

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