| The Families of Angiosperms |
L. Watson and M.J.Dallwitz
IncludingTribulaceae Trautv.,Tetradiclidaceae; excludingBalanitaceae,Nitrariaceae,Peganaceae.
Habit and leaf form.Trees, orshrubs (mostly, sometimes with short-shoots), or herbs (often with jointednodes); resinous, or not resinous. ‘Normal’ plants, or switch-plants(sometimes, more or less); sometimes more or less phyllodineous (e.g., speciesin which the leaflets fall before the photosynthesising petioles). Plantssucculent, or non-succulent. The herbs perennial (mostly), or annual (somespecies ofKallstroemia,Tribulus andZygophyllum).Xerophytic (and often halophytic, in salt-deserts).Leavesopposite (usually), or alternate (e.g.Viscainoa); when alternate,spiral; ‘herbaceous’, or leathery, or fleshy, or modified into spines;petiolate (mostly), or sessile (e.g.Augea); non-sheathing; compound(nearly always), or simple (supposedly, e.g. in someZygophyllum andFagonia species); pulvinate, or epulvinate;usuallyunifoliolate, or bifoliolate, or ternate, or pinnate; when pinnate,paripinnate. Leaflets pulvinate, or epulvinate. Lamina one-veined, or pinnatelyveined; cross-venulate (small veins often terminating in dilated tracheids).Leavesstipulate.Stipulesfree of one another;spiny (often), or scaly, or leafy;persistent. Leaf development not‘graminaceous’.
Leaf anatomy.The leaflamina dorsiventral (usually), or bifacial, or centric. Mucilaginousepidermis present, or absent. Stomata mainly confined to one surface, or on bothsurfaces; anomocytic (mostly), or paracytic, or actinocytic. Hairs present, orabsent (Augea); eglandular, or glandular; when present, unicellular(mostly), or multicellular. Unicellular hairs branched (rarely, two-armed), orsimple (mostly). Multicellular hairs branched, or simple. Complex hairs present,or absent; when present, capitate. Adaxial hypodermis present, or absent. Themesophyll containing mucilage cells (e.g., inNitraria spp.), or notcontaining mucilage cells; with sclerenchymatous idioblasts (and then these alsocommon in stems), or without sclerenchymatous idioblasts; containing crystals.The crystals druses, or solitary-prismatic, or raphides (rarely). Minor leafveins without phloem transfer cells (Tribulus,Zygophyllum).
Axial (stem, wood) anatomy.Young stems with solid internodes (mostly), or with hollowinternodes (inZygophyllum fabago). Pith homogeneous (usually, consistingof thin-walled cells), or heterogeneous (sometimes containing stone cells).Secretory cavities absent. Cork cambium present; initially deep-seated, orinitially superficial (usually). Nodes tri-lacunar (with the lateral gapsassociated with a split trace and very closely opposed); commonly exhibiting oneither side a trace which divides, contributing the outermost lateral traces toeach of the opposite leaves (exemplified in five genera), or withoutsplit-lateral traces (?). Primary vascular tissues in a cylinder, withoutseparate bundles, or comprising a ring of bundles (then comprising closelyplaced bundles). Internal phloem absent. Secondary thickening developing from aconventional cambial ring, or anomalous.Primary medullary raysnarrow.
The wood semi-ring porous (rarely), or diffuse porous. The vessels small (tovery small, usually), or medium (Balanites andGuaiacum);solitary, or radially paired to in radial multiples, or clustered (notably so inBalanites). The vessel end-walls horizontal to oblique; simple. Thevessels without vestured pits; without spiral thickening. The axial xylem withtracheids, or without tracheids (?); often with vasicentric tracheids; withfibre tracheids, or without fibre tracheids; with libriform fibres, or withoutlibriform fibres; without septate fibres. The fibres without spiral thickening.The parenchyma usually typically apotracheal (diffuse or in uniseriate bands),or paratracheal (Bulnesia). The secondary phloem not stratified.‘Included’ phloem absent. The wood storied (in most genera).
Reproductive type, pollination.Unisexual flowers present, or absent. Plants hermaphrodite (mostly),or dioecious (Neoluederitzia). Pollination entomophilous.
Inflorescence, floral, fruit and seedmorphology.Flowers solitary, or aggregated in‘inflorescences’; when solitary, terminal, or axillary (orleaf-opposed). The ultimate inflorescence units when flowers aggregated, cymose.Inflorescences terminal, or axillary, or leaf-opposed.Flowersebracteate;ebracteolate; regular;not resupinate;(4–)5(–6) merous; cyclic; tetracyclic, or pentacyclic, orpolycyclic. Floral receptacle developing a gynophore, or with neither androphorenor gynophore.Free hypanthiumabsent. Hypogynous disk present(usually), or absent (sometimes with nectariferous glands between the perianthwhorls as well as or instead of those between stamens and ovary); when present,extrastaminal (usually), or intrastaminal; of separate members, or annular.
Perianth with distinct calyx and corolla (usually), or sepaline (thecorolla sometimes lacking, e.g.Seetzenia); (4–)5, or(8–)10(–12); (1–)2 whorled; isomerous. Calyx(4–)5(–6); 1 whorled; polysepalous, or gamosepalous; regular;imbricate (usually), or valvate.Corolla when present,(4–)5(–6); 1 whorled;polypetalous; imbricate, or contorted,or valvate (rarely); regular; white, or yellow, or red, or blue (rarely).
Androecium (4–)5, or 10, or 15. Androecial members free of theperianth; free of one another; 1–3 whorled. Androecium exclusively offertile stamens, or including staminodes (e.g. inTribulus, where theantesepalous whorl may be sterile). Staminodes when present, 4, or 5; externalto the fertile stamens.Stamens(4–)5, or 10, or 15;isomerous with the perianth, or diplostemonous, or triplostemonous;alternisepalous, or oppositisepalous (when the outer whorl isstaminodal); alternating with the corolla members, or both alternating withand opposite the corolla members. Filaments appendiculate (commonly, with basalligular scales which may unite to form an appendage within the staminal ring),or not appendiculate.Anthersdorsifixed; versatile; dehiscing vialongitudinal slits; introrse, or latrorse; tetrasporangiate. Endotheciumdeveloping fibrous thickenings. Anther epidermis persistent. Microsporogenesissimultaneous. The initial microspore tetrads tetrahedral, or isobilateral, ordecussate. Anther wall initially with one middle layer, or initially with morethan one middle layer (up to 3); of the ‘dicot’ type. Tapetumglandular. Pollen grains aperturate; 3 aperturate, or 4–20 aperturate (to‘polyforate’); colpate, or porate, or colporate, or foraminate, orrugate; 2-celled (in 4 genera), or 3-celled (Tribulus only).
Gynoecium (2–)5(–6) carpelled. Carpels isomerous with theperianth (usually), or reduced in number relative to the perianth, or increasedin number relative to the perianth. The pistil (2–)4–12 celled.Gynoecium syncarpous;eu-syncarpous; superior. Ovary(2–)5(–6) locular (but sometimes these secondarily partitioned).Locules secondarily divided by ‘false septa’ (inTribulus), orwithout ‘false septa’. Ovary sessile, or subsessile, or stipitate (inseveral New World genera). Gynoecium non-stylate, or stylate.Styles 1;attenuate from the ovary; apical. Stigmas 1; lobed or capitate; wet type,or dry type; papillate; Group II type, or Group III type.Placentationaxile.Ovules 1–50 per locule (to ‘several’ or to‘many’);pendulous; apotropous; with ventral raphe;non-arillate; anatropous (usually), or hemianatropous, or orthotropous, orcampylotropous; bitegmic; crassinucellate. Outer integument contributing to themicropyle, or not contributing to the micropyle. Endothelium differentiated, ornot differentiated. Embryo-sac developmentPolygonum-type. Polar nucleifusing prior to fertilization. Antipodal cells formed; 3; not proliferating;ephemeral (usually), or persistent. Synergids pear-shaped. Endosperm formationnuclear. Embryogeny solanad.
Fruit non-fleshy (usually), or fleshy; dehiscent (usually), orindehiscent, or a schizocarp. Mericarps when schizocarpic, 2–5; theseindehiscent ‘cocci’, often angular, winged or spiny.Fruitwhen non-schizocarpic,a capsule (usually), orcapsular-indehiscent.Capsulessepticidal, or loculicidal, orsepticidal and loculicidal. Fruit elastically dehiscent (when of cocci), orpassively dehiscent. Seeds endospermic, or non-endospermic. Endosperm oily.Cotyledons 2. Embryo chlorophyllous (3/3); straight, or curved.
Seedling.Germinationphanerocotylar, or cryptocotylar.
Physiology, phytochemistry.C3, or C4. C3physiology recorded directly inBulnesia,Fagonia,Guaiacum,Kallstroemia,Larrya,Neoluederitzia,Porlieria,Seetzenia,Sisyndite,Viscainoa,Zygophyllum. C4 physiology recorded directly inKallstroemia,Tribulus,Zygophyllum.AnatomyC4 type (Tribulus,Zygophyllum: see illustration),or non-C4 type (Zygophyllum). Sugars transported assucrose (inBulnesia).Mustard-oilspresent. Notcyanogenic. Alkaloids present (commonly), or absent. Iridoids not detected.Saponins/sapogenins present (commonly), or absent. Proanthocyanidins absent.Flavonols present; kaempferol and quercetin. Ellagic acid absent(Zygophyllum). Aluminium accumulation not found.
Geography, cytology.Temperate totropical. Widespread tropical, subtropical and warm temperate, often in drierareas.X = 6, 8–13(+).
Taxonomy.Subclass Dicotyledonae;Crassinucelli. Dahlgren’s Superorder Corniflorae; Cornales.Cronquist’s Subclass Rosidae; Sapindales. APG III core angiosperms; coreeudicot; Superorder Rosanae; fabid. APG IV Order Zygophyllales.
Species 235. Genera about 30;Augea,Bulnesia,Fagonia,Guaiacum,Halimiphyllum,Izozogia,Kallstroemia,Kelleronia,Larrea,Metharme,Miltianthus,Morkillia,Neoluederitzia,Pintoa,Plectrocarpa,Porlieria,Roepera,Sarcozygium,Seetzenia,Sericodes,Sisyndite,Tetradiclis (APGNitrariaceae),Tetraena,Tribulopis,Tribulus,Viscainoa,Zygophyllum.
General remarks.Analyses of rbcLsequence and other data (see Sheahan and Chase 1996) resulted in removal of thetruly sapindaleanNitraria (Nitrariaceae) andPeganum andMalacocarpus (Peganaceae), but left the affinities ofZygophyllaceae s. str. in doubt. TherbcL sequence data (see alsoChaseet al. 1993, Gadeket al 1996) linkedZygophyllaceaeloosely withKrameria and the Polygalales, associating them withRosiflorae rather than Rutiflorae. Some of the above variation attributed hereto characters ignored by Sheahan and Chase (e.g., in anther development,embryology and pollen structure) may now be spurious ........
Economic uses, etc.Guaiacumofficinale is the source of the hardest, densest wood (lignum vitae);Guaiacum,Zygophyllum,Tribulus andLarrea speciesare cultivated in warm regions as ornamentals; and this family is said toinclude the few plants poisonous to camels.
Illustrations.• Fagonia arabica: Kirtikar & Basu, Indian MedicinalPlants 1 (1918). • Guaiacumofficinale: Köhler’s Medizinal-Pflanzen 2 (1890). • Guaiacum officinale: Bot. Reg. 9 (1839).• Kallstroemia maxima: Fawcett &Rendle, Flora of Jamaica 4 (1920). • cf. Kallstroemia tribuloides, as Ehrenbergia:Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Tetraena alba, as Zygophyllum amblyocarpum: Hook.Ic. Pl. 24 (1895). • Tribuluscistoides: Fawcett & Rendle, Flora of Jamaica 4 (1920). • Le Maout and Decaisne: Tribulus terrestris.• Le Maout and Decaisne: Zygophyllum,Seetzenia. • Zygophyllum insuave:Bot. Mag. 372 (1797). • Zygophyllum foetidum: Bot. Mag. 372 (1797),text. • Leaf hairs of Fagonia andLarrea, and leaf TS of Tribulus alatus: Solereder, 1908.
We advise against extracting comparative informationfrom the descriptions. This is much more easily achieved using theDELTA data files or theinteractive key, which allows access to the characterlist, illustrations, full and partial descriptions, diagnostic descriptions,differences and similarities between taxa, lists of taxa exhibiting or lackingspecified 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 alsoGuidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., andDallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions,illustrations, identification, and information retrieval. Version: 25th March2025.delta-intkey.com’.
