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The families of flowering plants

L. Watson and M.J. Dallwitz

Burseraceae Kunth

Including Balsameaceae Dum.

Habit and leaf form. Trees, or shrubs; bearing essential oils (in the bark); resinous. Leaves alternate; spiral, or distichous (rarely); petiolate; non-sheathing; gland-dotted (rarely), or not gland-dotted; aromatic (resinous, but usually not punctate); compound; pinnate, or ternate, or unifoliolate (rarely). Lamina pinnately veined; cross-venulate. Leaves exstipulate (usually), or stipulate (rarely); leaf development not ‘graminaceous’. Domatia occurring in the family (found in one genus); manifested as pits, or hair tufts.

Leaf anatomy. The leaf lamina dorsiventral (usually, with a single palisade layer), or bifacial. Mucilaginous epidermis present (commonly), or absent. Stomata present; mainly confined to one surface, or on both surfaces (always more numerous abaxially); anomocytic. Hairs present; eglandular (of diverse forms, see illustration), or eglandular and glandular (the capitate glandular hairs variously short- or long-stalked, sometimes snail-shaped). Adaxial hypodermis present, or absent (usually). Lamina usually with secretory cavities (in the phloem). Secretory cavities containing resin. The mesophyll containing mucilage cells, or not containing mucilage cells. Minor leaf veins without phloem transfer cells (Commiphora).

Axial (stem, wood) anatomy. Pith homogeneous, or heterogeneous (usually lignified). Secretory cavities present (usually, in the phloem, rarely in the pith: see illustration); with resin (“balsam”). Cork cambium present; initially superficial (usually), or initially deep-seated (in Santiria). Nodes multilacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles present (e.g., in Canarium), or absent (usually). Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels usually relatively small, or medium; commonly solitary, radially paired, in radial multiples, and clustered, or in tangential arcs (rarely). The vessel end-walls simple. The vessels without vestured pits; without spiral thickening. The axial xylem with libriform fibres; at least sometimes including septate fibres, or without septate fibres (?). The fibres without spiral thickening. The parenchyma paratracheal. The secondary phloem not stratified. ‘Included’ phloem absent. The wood storied to partially storied, or not storied.

Reproductive type, pollination. Plants hermaphrodite, or dioecious, or polygamomonoecious.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, in racemes, and in heads. Inflorescences often in thyrses. Flowers small; regular; 3–5 merous; cyclic; tetracyclic, or pentacyclic. Hypogynous disk present, or absent.

Perianth with distinct calyx and corolla (usually), or sepaline (corolla sometimes lacking); 6–10; normally 2 whorled; isomerous. Calyx (3–)4, or 5; 1 whorled; gamosepalous (the sepals usually basally connate); regular; imbricate, or valvate. Corolla when present, (3–)4, or 5; 1 whorled; polypetalous, or gamopetalous (rarely); imbricate, or valvate; regular.

Androecium 3–5, or 6–10. Androecial members free of the perianth; markedly unequal (often, when two whorls), or all equal; free of one another (usually), or coherent (rarely); when coherent 1 adelphous (via connate filaments); 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens 4–5, or 8–10; diplostemonous (usually), or isomerous with the perianth; when one whorled, alternisepalous. Anthers dorsifixed (slightly), or basifixed; versatile (slightly), or non-versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged, or unappendaged. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads usually tetrahedral. Anther wall initially with one middle layer, or initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; commonly 3 aperturate; commonly colporate; 2-celled.

Gynoecium (2–)3–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil (2–)3–5 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary (2–)3–5 locular. Styles 1. Placentation axile. Ovules (1–)2 per locule; pendulous; epitropous (micropyle superior); with ventral raphe; non-arillate; hemianatropous; 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. Synergids hooked. Endosperm formation nuclear.

Fruit fleshy, or non-fleshy; indehiscent (usually), or dehiscent; a drupe (usually, or drupelike), or a capsule (rarely). The drupes with separable pyrenes, or with one stone. Seeds non-endospermic (or almost so); wingless. Cotyledons 2. Embryo chlorophyllous (2/2); straight or rolled.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. C3. Sugars transported as sucrose (in Bursera). Alkaloids present, or absent (mostly). Iridoids not detected. Saponins/sapogenins present, or absent (rarely). Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (Protium). Aluminium accumulation not found.

Geography, cytology. Sub-tropical and tropical. Widespread. X = 11, 13, 23.

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 500. Genera 17; Aucoumea, Beiselia, Boswellia, Bursera, Canarium, Commiphora, Crepidospermum, Dacryodes, Garuga, Haplolobus, Pachylobus, Protium, Santiria, Scutinanthe, Tetragastris, Trattinnickia, Triomma.

Illustrations. • Technical details: Dacryodes: (Thonner). • Technical details: Bursera, Protium (Lindley). • Boswellia odorata: Hook. Ic. Pl. 30 (1913). • Canarium pilosum, as C. hirtellum: Hook. Ic. Pl. 16 (1866). • Commiphora playfairii, as Balsamodendrum: Hook. Ic. Pl. 26 (1897). • Commiphora woodii, as C. caryifolia: Hook. Ic. Pl. 23 (1894). • Dacryodes edulis, as Pachylobus: Hook. Ic. Pl. 26 (1898). • Protium guianense: Hook. Ic. Pl. 16 (1887). • Triomma malaccensis: Hook. Ic. Pl. 29 (1906). • Leaf hairs of Boswellia, Canarium, Crepidospermum, Protium, Santiria (Solereder, 1908). • TS stem of Boswellia, showing balsam canals in phloem and pith: 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: 20th June 2017.’.