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The families of flowering plants

L. Watson and M.J. Dallwitz

Euphorbiaceae Juss.

Including Acalypheae (Acalyphaceae) J.G. Agardh, Bertyaceae J.G. Agardh, Columellaceae Dulac (p.p.), Crotonaceae J.G. Agardh, Hippomaneae (Hippomanaceae) J.G. Agardh, Micrantheae (Micrantheaceae) J.G. Agardh, Oldfieldiaceae auctt., Picrodendraceae s. lat., Phyllantheae (Phyllanthaceae) J.G. Agardh, Putranjiveae (Putranjivaceae) Endl., Porantheraceae (Pax) Hurusawa, Pseudanthaceae Endl., Ricinaceae Barkley, Ricinocarpaceae (Pax) Hurusawa, Scepaceae Lindl., Tithymaloideae (Tithymalaceae) Vent., Treviaceae Bullock, Trewiaceae Lindl.; excluding Androstachydaceae, Bischofiaceae, Hymenocardiaceae, Peraceae p.p., Picrodendraceae s. str., Stilaginaceae, Uapacaceae.

Habit and leaf form. Trees, or ‘arborescent’, or shrubs, or herbs, or lianas; laticiferous (Euphorbioideae), or non-laticiferous, without coloured juice (e.g. Phyllanthoideae), or with coloured juice (rarely). ‘Normal’ plants, or switch-plants; often with the principal photosynthesizing function transferred to stems, or phyllodineous, or ‘cactoid’, with succulent, photosynthetic stems (often). Leaves well developed, or much reduced. Plants succulent, or non-succulent; green and photosynthesizing. Self supporting, or climbing. Mesophytic, or xerophytic. Leaves minute to large; alternate (usually), or opposite to whorled (rarely); spiral, or distichous; ‘herbaceous’, or leathery, or fleshy, or membranous, or modified into spines; petiolate to sessile; non-sheathing; gland-dotted, or not gland-dotted; simple (usually), or compound; not peltate; when compound, palmate. Lamina entire; pinnately veined, or palmately veined. Leaves stipulate (nearly always, but the stipules sometimes reduced to branched hairlike structures, or to glands). Stipules scaly, or leafy, or spiny, or represented by glands; caducous, or persistent. Leaf development not ‘graminaceous’. Domatia occurring in the family (known from 7 genera); manifested as pits, or pockets, or hair tufts (rarely).

General anatomy. Plants with laticifers (commonly, articulated or non-articulated), or without laticifers (absent notably from the Phyllanthoideae).

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface, or on both surfaces; anomocytic, or anisocytic, or paracytic. Hairs of numerous kinds present (in the family: see illustrations); eglandular and glandular. Urticating hairs present (in a few lianes), or absent. Lamina without secretory cavities. The mesophyll with sclerenchymatous idioblasts, or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Euphorbia).

Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated (rarely), or initially superficial. Nodes unilacunar, or tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles (commonly), or comprising a ring of bundles (e.g., in succulent Euphorbias); collateral, or bicollateral. Internal phloem present (in numerous genera), or absent. Cortical bundles present (occasionally), or absent. Medullary bundles present (occasionally), or absent. Secondary thickening developing from a conventional cambial ring (mostly, even in lianes), or anomalous. The anomalous secondary thickening via concentric cambia, or from a single cambial ring. Primary medullary rays wide, or mixed wide and narrow, or narrow.

The vessel end-walls scalariform, or simple (usually). The vessels with vestured pits (rarely), or without vestured pits. The axial xylem with libriform fibres; including septate fibres (e.g., in some Phyllanthoideae), or without septate fibres. The parenchyma apotracheal, or paratracheal (or very sparse, or absent). The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones (very rarely. e.g. in Bridelia), or not stratified. ‘Included’ phloem present (occasionally, e.g. Dalechampia), or absent.

Reproductive type, pollination. Plants monoecious, or dioecious, or hermaphrodite (very rarely: species of Drypetes, Aporosa). Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. The ultimate inflorescence units nearly always cymose (commonly the first branching racemose, with all the subsequent branching cymose). Inflorescences terminal, or axillary; with involucral bracts, or without involucral bracts; pseudanthial, or not pseudanthial. Flowers bracteate, or ebracteate (?); minute, or small, or medium-sized; regular. Free hypanthium absent. Hypogynous disk present (commonly), or absent; of separate members, or annular.

Perianth sepaline, or vestigial, or absent, or petaline (occasionally); when present, (3–)5–6(–12); free, or joined; 1 whorled (usually), or 2 whorled (sometimes — e.g. Jatropha); when two-whorled, isomerous. Calyx 5; polysepalous, or gamosepalous; regular. Corolla when present, 5; polypetalous; regular.

Androecium 1–1000 (i.e. to ‘many’). Androecial members branched (e.g. Ricinus), or unbranched; free of the perianth; free of one another, or coherent (may be free or united in a variety of ways). Androecium exclusively of fertile stamens. Stamens 1–1000; reduced in number relative to the adjacent perianth to polystemonous; erect in bud, or inflexed in bud. Anthers dehiscing via longitudinal slits, or dehiscing via pores (rarely with apical pores); extrorse, or introrse; bilocular to four locular; bisporangiate, or tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer, or initially with more than one middle layer; of the ‘dicot’ type, or of the ‘monocot’ type. Tapetum amoeboid, or glandular. Pollen grains aperturate, or nonaperturate (rarely); 3 aperturate (commonly), or 4–30 aperturate (?); colpate, or colporate, or foraminate, or rugate; 2-celled (13 genera), or 3-celled (4 genera), or 2-celled and 3-celled (with both states in Euphorbia).

Gynoecium (2–)3 carpelled, or 4–30 carpelled (rarely). The pistil (2–)3 celled, or 4–30 celled (rarely). Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary (2–)3 locular, or 4–30 locular (rarely). Styles 3 (usually), or 6(–12) (or more); free, or partially joined (to almost completely joined, in the Phyllantheae); apical. Stigmas 3 (usually), or 6(–12) (or more); dry type; papillate, or non-papillate; Group II type. Placentation axile, or apical. Ovules 1 per locule, or 2 per locule; pendulous; mostly epitropous; with ventral raphe (usually), or with dorsal raphe; when two, collateral; arillate (often carunculate, the caruncle often covering the micropyle, the caruncle often covering the micropyle), or non-arillate; orthotropous, or anatropous, or hemianatropous; bitegmic; crassinucellate. Outer integument usually contributing to the micropyle. Embryo-sac development Polygonum-type, or Allium-type, or Drusa-type, or Fritillaria-type, or Penaea-type. Antipodal cells formed; initially 3; proliferating (to 5 cells, in Jatropha), or not proliferating. Synergids pear-shaped, or hooked (rarely with filiform apparatus). Hypostase present. Endosperm formation nuclear. Embryogeny onagrad (usually), or solanad, or piperad.

Fruit non-fleshy (usually), or fleshy; dehiscent, or indehiscent, or a schizocarp (usually). Mericarps when schizocarpic, (2–)3 (usually, usually dehiscent), or 4–30 (?). Fruit when non-schizocarpic, a capsule, or a drupe; elastically dehiscent (schizocarpic capsules often splitting elastically), or passively dehiscent. Seeds endospermic (nearly always). Endosperm oily. Cotyledons 2 (usually wider than the radicle); flat, or folded. Embryo chlorophyllous (4/6), or achlorophyllous (8/10 — Euphorbia being variable); straight, or curved.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. C3, C4, and CAM. C3 physiology recorded directly in Argythamnia, Euphorbia, Phyllanthus, Ricinus. C4 physiology recorded directly in Chamaesyce, Euphorbia. CAM recorded directly in Euphorbia, Monadenium, Pedilanthus, Synadenium. Anatomy C4 type (Euphorbia), or non-C4 type (Acalypha, Dalechampia, Croton, Euphorbia, Hevea, Jatropha, Manihot, Meineckia, Micrococca, Phyllanthus, Ricinus, Tragia, Tragiella). Sugars transported as sucrose (e.g. in Aleurites, Sapium), or as sugar alcohols + oligosaccharides + sucrose (e.g. Phyllanthus, Ricinus). Inulin recorded (Aleurites, Gibbs 1974). Mustard-oils present (Drypetes, Putranjiva), or absent. Cyanogenic, or not cyanogenic. Cynogenic constituents tyrosine-derived, or phenylalanine-derived (?), or of Hegnauer’s ‘Group C’. Alkaloids present (commonly), or absent. Anthraquinones detected (Clutia); polyacetate derived. Arbutin absent. Iridoids not detected. Saponins/sapogenins present (rarely), or absent. Proanthocyanidins present (rarely), or absent; when present, cyanidin and delphinidin (in one Phyllanthus species). Flavonols present, or absent; kaempferol, or kaempferol and quercetin. Ellagic acid present (4 species, 3 genera), or absent (8 species, 5 genera). Aluminium accumulation demonstrated (but in relatively few genera), or not found.

Geography, cytology. Temperate, sub-tropical, and tropical. Cosmopolitan, except Arctic. X = 6–14 (or more).

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Euphorbiales. Cronquist’s Subclass Rosidae; Euphorbiales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Malpighiales.

Species 5000. Genera about 300; Acalypha, Acidocroton, Acidoton, Actephila, Adelia, Adenochlaena, Adenocline, Adenopeltis, Adenophaedra, Adriana, Aerisilvaea, Afrotrewia, Agrostistachys, Alchornea, Alchorneopsis, Aleurites, Algernonia, Alphandia, Amanoa, Amperea, Amyrea, Andrachne, Angostyles, Annesijoa, Anomalocalyx, Anthostema, Aparisthium, Apodiscus, Aporusa, Argomuellera, Argythamnia, Aristogeitonia, Ashtonia, Astrocasia, Astrococcus, Austrobuxus, Avellanita, Baccaurea, Baliospermum, Baloghia, Benoistia, Bernardia, Bertya, Beyeria, Blachia, Blotia, Blumeodendron, Bocquillonia, Bonania, Borneodendron, Bossera, Botryophora, Breynia, Bridelia, Calycopeplus, Canaca, Caperonia, Caryodendron, Casabitoa, Calvacoa, Celaenodendron, Celianella, Cephalocroton, Cephalomappa, Chaetocarpus, Chascotheca, Cheilosa, Chiropetalum, Chlamydojatropha, Chondrostylis, Chonocentrum, Choriceras, Chrozophora, Cladogelonium, Cladogynos, Claoxylon, Claoxylopsis, Cleidiocarpon, Cleidion, Cleistanthus, Clutia, Cnesmone, Cnidoscolus, Cocconerion, Codiaeum, Colliguaja, Conceveiba, Cordemoya, Croizatia, Croton, Crotonogyne, Crotonogynopsis, Crotonopsis, Ctenomeria, Cubanthus, Cyrtogonone, Cyttaranthus, Dalechampia, Dalembertia, Deuteromallotus, Deutzianthus, Dichostemma, Dicoelia, Didymocistus, Dimorphocalyx, Discocarpus, Discoclaoxylon, Dicocleidion, Discoglypremna, Dissiliaria, Ditaxis, Ditta, Dodecastigma, Domohinea, Doryxylon, Droceloncia, Drypetes, Duvigneaudia, Dysopsis, Elaeophorbia, Elateriospermum, Eleutherostigma, Endadenium, Endospermum, Enriquebeltrania, Epiprinus, Eremocarpus, Erismanthus, Erythrococca, Euphorbia, Excoecaria, Fahrenheitia, Flueggea, Fontainea, Garcia, Gavarretia, Givotia, Glochidion, Glycydendron, Glyphostylus, Grimmeodendron, Grossera, Gymnanthes, Haematostemon, Hamilcoa, Hevea, Heywoodia, Hippomane, Homonoia, Hura, Hyaenanche, Hieronima, Hylandia, Jablonskia, Jatropha, Joannesia, Kairothamnus, Keayodendron, Klaineanthus, Koilodepas, Lachnostylis, Lasiococca, Lasiocroton, Lautembergia, Leeuwenbergia, Leidesia, Leptonema, Leptopus, Leucocroton, Lingelsheimia, Lobanilia, Loerzingia, Longetia, Mabea, Macaranga, Maesobotrya, Mallotus, Manihot, Manihotoides, Manniophyton, Maprounea, Mareya, Mareyopsis, Margaritaria, Martretia, Megistostigma, Meineckia, Melanolepis, Mercurialis, Micrandra, Micrandropsis, Micrantheum, Micrococca, Microstachys, Mildbraedia, Mischodon, Moacroton, Monadenium, Monotaxis, Moultonianthus, Myladenia, Myricanthe, Nealchornea, Necepsia, Neoboutonia, Neoguillauminia, Neoholstia, Neoroepera, Neoscortechinia, Neotrewia, Octospermum, Oldfieldia, Oligoceras, Omalanthus, Omphalea, Omphellantha, Ophthalmoblapton, Oreoporanthera, Ostodes, Pachystroma, Pachystylidium, Pantadenia, Paradrypetes, Paranecepsia, Parapantadenia, Parodiodendron, Pausandra, Pedilanthus, Pentabrachion, Petalodiscus, Petalostigma, Philyra, Phyllanoa, Phyllanthus, Pimelodendron, Piranhea, Plagiostyles, Platygyna, Plukenetia, Podadenia, Podocalyx, Pogonophora, Poilaniella, Poinsettia, Polyandra, Poranthera, Protomegabaria, Pseudagrostistachys, Pseudanthus, Pseudocroton, Pseudolachnostylis, Pterococcus, Ptychopyxis, Putranjiva, Pycnocoma, Reutealis, Reverchonia, Richeria, Richeriella, Ricinocarpus, Ricinodendron, Ricinus, Rockinghamia, Romanoa, Sagotia, Sampantea, Sandwithia, Sapium, Sauropus, Savia, Scagea, Schinziophyton, Sebastiania, Securinega, Seidelia, Senefeldera, Senefelderopsis, Sibangea, Spathiostemon, Speranksia, Sphaerostylis, Sphyranthera, Spirostachys, Spondianthus, Stachyandra, Stachystemon, Stillingia, Strophioblachia, Sumbaviopsis, Suregada, Symphyllia, Synandenium, Syndyophyllum, Tacaruna, Tannodia, Tapoides, Tetracoccus, Tetraplandra, Tetrorchidium, Thecacoris, Thyrsanthera, Tragia, Tragiella, Trevia, Trigonopleura, Trigonostemon, Vaupesia, Vernicia, Vigia, Voatamalo, Wetria, Whyanbeelia, Wielandia, Zimmermannia, Zimmermanniopsis.

General remarks. This attempted description of a relatively sensu stricto version of Euphorbiaceae probably under-estimates variation, so recognition of segregate families and synonyms (see above) in this circle of affinity needs to be competently re-assessed. Comparisons via Intkey of this description with those of the segregates currently offered in this package imply there is some justification for recognizing most of them; but cavalier APG recommendations in this connection are accompanied by hopelessly inadequate, non-comparative descriptions with no keys and no assignment of essential 'esoteric characters' (cf. Christenhusz et al (2017).

Economic uses, etc. Commercial products include rubber (Hevea), tung oil (Aleurites), castor oil (Ricinus), and cassava and tapioca (Manihot). Many ornamentals, especially from Euphorbia (poinsettia, etc.), Codiaeum (croton), Phyllanthus (Otaheite gooseberry).

Illustrations. • Le Maout and Decaisne: Amperea, Ricinocarpos. • Le Maout and Decaisne: Poranthera, Pseudanthus. • Le Maout and Decaisne: Xylophylla (= Phyllanthus), Bridelia, Ricinus, Stillingia. • Le Maout and Decaisne: Mercurialis, Ditaxis, Cluytia (= Clutia), Baliospermum. • Le Maout and Decaisne: Hippomane, Hura, Calycopeplus, Caelebogyne. • Le Maout and Decaisne: Euphorbia. • Aporusa cardiosperma, as Scepa lindleyana: Wight’s Figs. of Indian Plants 2 (1843). • Euphorbia alata: Hook. Ic. Pl. 7–8 (1844). • Euphorbia cf. characias: as E. veneta, Bot. Reg. XXIV, 6 (1838). • Euphorbia amydaloides: Eng. Bot. 1260, 1868. • Euphorbia helioscopia and E. coralloides: Eng. Bot. 1245 and 1259, 1868. • Euphorbia peplus and E. exigua: Eng. Bot. 1265 and 1266, 1868. • Euphorbia paralias and E. portlandica: Eng. Bot. 1263 and 1264, 1868. • Euphorbia sphaerorhiza: Hook. Ic. Pl. 4 (1841). • Euphorbia lathyris (J. E. Sowerby, 1861). • Euphorbia rigida: Bot. Reg. XXIV, 43 (1838). • Euphorbia, Mercurialis (B. Ent. compilation, 1824–35). • Aristogeitonia limoniifolia: Hook. Ic. Pl. 30 (1911). • Jatropha dioica, as Mozinna spathulata: Hook. Ic. Pl. 4 (1841). • Klaineanthus gaboniae: Hook. Ic. Pl. 30 (1913). • Bridelia pervilleana var. humbertii, B. tulasneana: Humbert, Fl. Madagascar & Comores 1 (1958). • Cleistanthus boivianus, C. perrieri, C. stentonia: Humbert, Fl. Madagascar & Comores 1 (1958). • Cleistanthus boivianus, C. occidentalis, Bridelia pervilleana: Humbert, Fl. Madagascar & Comores 1 (1958). • Lachnostylis hirta: Hook. Ic. Pl. 13 (1877–79). • Lingelsheimia manongarivensis, L. ambigua, L. fiherensis (as Danguodrypetes): Humbert, Fl. Madagascar & Comores 1 (1958). • Mercurialis annua (B. Ent., 1828). • Mercurialis perennis (J. E. Sowerby, 1861). • Mercurialis perennis and M. annua: Eng. Bot. 1268 and 1269, 1868. • Phyllanthus floribundus: Thonner. • Phyllanthus comorensis, P. humbertianus, P. seyrigii, P. decipiens var. bolivianus: Humbert, Fl. Madagascar & Comores 1 (1958). • Phyllanthus gaudotianus (= ?), P. nummulariaefolius, P. vergens, P. cryptophilus: Humbert, Fl. Madagascar & Comores 1 (1958). • Putranjiva roxburghii: Brandis, Ill. Forest Flora of N.W. & Central India (1874). • Sibangea arborescens: Hook. Ic. Pl. 15 (1883). • Drypetes sp. (inc. Hemicyclia), Sibangea arborescens and Putranjiva roxburghii, with Petalostigma (Picrodendraceae): Nat. Pflanzenfam. 3 (1896). • Drypetes capuronii, D. grandiflora, D. stipulacea: Humbert, Fl. Madagascar & Comores 1 (1958). • Drypetes coriifolia, D. ambigua, D oppositifolia: Humbert, Fl. Madagascar & Comores 1 (1958). • Drypetes madagascariensis: Humbert, Fl. Madagascar & Comores 1 (1958). • Croton, Plukenetia, Tragia: leaf hairs (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: 15th April 2018.’.