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The families of flowering plants

L. Watson and M.J. Dallwitz

Pedaliaceae R. Br.

Including Sesamaceae R. Br. ex Berchtold & Presl; excluding Martyniaceae, Trapellaceae.

Habit and leaf form. Herbs (mostly), or shrubs (rarely). Mesophytic to xerophytic (mostly inhabiting shores and deserts). Leaves opposite (at least below); simple. Lamina dissected, or entire; when dissected, pinnatifid, or runcinate; pinnately veined; cross-venulate. Leaves exstipulate.

Leaf anatomy. The leaf lamina dorsiventral. Hydathodes present (sometimes), or absent. Stomata present; mainly confined to one surface (abaxial), or on both surfaces (mostly); anomocytic. Hairs present; eglandular and glandular (with capitate, short-stalked mucilage hairs occurring universally; and hairs with long or short unicellular or uniseriate stalks and spherical or turbinate heads, and long uniseriate non-glandular trichomes recorded in several genera); mostly multicellular. The mesophyll containing crystals. The crystals small, druses and solitary-prismatic. Minor leaf veins without phloem transfer cells (Ceratotheca).

Axial (stem, wood) anatomy. Pith with diaphragms (sometimes, in Pedalium), or without diaphragms. Cork cambium present; initially superficial. Primary vascular tissues collateral. Secondary thickening developing from a conventional cambial ring. Primary medullary rays mixed wide and narrow.

The vessel end-walls simple. The axial xylem with libriform fibres. The wood partially storied (VPI).

Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes. The ultimate inflorescence units cymose. Inflorescences axillary; dichasia or cymes. Flowers bracteate (the bracts with axillary abortive flowers functioning as nectaries); very irregular. The floral irregularity involving the perianth and involving the androecium. Flowers 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous (forming a lobed tube); blunt-lobed; with the median member posterior. Corolla 5; 1 whorled; gamopetalous; imbricate; unequal but not bilabiate, or bilabiate; spurred (sometimes), or not spurred.

Androecium 5. Androecial members adnate (to the corolla tube); markedly unequal; free of one another; 1 whorled. Androecium including staminodes. Staminodes 1 (the posterior member); in the same series as the fertile stamens; representing the posterior median member; non-petaloid. Fertile stamens representing the posterior-lateral pair and the anterior-lateral pair. Stamens 4; inserted near the base of the corolla tube; didynamous; reduced in number relative to the adjacent perianth; oppositisepalous; alternating with the corolla members. Anthers connivent (in pairs), or separate from one another; dehiscing via longitudinal slits; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate, or T-shaped. Anther wall initially with more than one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen shed in aggregates (Sesamothamnus), or shed as single grains; when aggregated, in tetrads. Pollen grains aperturate; (3–)5–15 aperturate; colpate; 2-celled.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2–8 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 2–4 locular (but often with false septa). Locules secondarily divided by ‘false septa’, or without ‘false septa’. Gynoecium median; stylate. Styles 1; attenuate from the ovary; much longer than the ovary. Stigmas 1–2; 2 lobed; wet type; papillate; Group III type. Placentation axile. Ovules 1 per locule (Josephinia), or 2–50 per locule (to ‘many’); pendulous, or horizontal, or ascending; anatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped (elongated). Hypostase present. Endosperm formation cellular. Endosperm haustoria present; chalazal and micropylar. Embryogeny onagrad.

Fruit non-fleshy (often with hooks, or prickly); dehiscent, or indehiscent; a capsule, or a nut. Capsules loculicidal. Seeds thinly endospermic, or non-endospermic. Endosperm oily. Seeds with amyloid. Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Not cyanogenic. Verbascosides detected (2 genera). Iridoids detected; ‘Route II’ type (normal and decarb.). Saponins/sapogenins absent. Proanthocyanidins absent. Ellagic acid absent. Aluminium accumulation not found.

Special distinguishing feature. The funicles not as in Acanthaceae.

Geography, cytology. Sub-tropical to tropical. Africa, Madagascar, India, Southeast Asia, Malaysia, Australia.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Lamiiflorae; Scrophulariales. Cronquist’s Subclass Asteridae; Scrophulariales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order Lamiales.

Species 50. Genera 13; Ceratotheca, Dicerocaryum, Harpagophytum, Holubia, Josephinia, Linariopsis, Pedaliodiscus, Pedalium, Pterodiscus, Rogeria, Sesamothamnus, Sesamum, Uncarina.

Economic uses, etc. Commercial edible oil from Sesamum (benne).

Illustrations. • Sesamum indicum: R. Wight 2 (1850). • Sesamum indicum: Bot. Mag. 41 (1814). • Le Maout and Decaisne: Sesamum, Pedalium. • Holubia saccata: Hook Ic. Pl. 15 (1884). • Pterodiscus luridus: Bot. Mag. 95 (1869). • Sesamum angolense: Thonner. • Fruits representing 10 genera of Pedaliaceae: Nat. Pflanzenfam. IV (1895).

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: 24th October 2017.’.