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The families of flowering plants

L. Watson and M.J. Dallwitz

Geraniaceae Juss.

Including Erodiaceae Horan., Rostraceae Dulac; excluding Biebersteiniaceae, Dirachmaceae, Hypseocharitaceae, Ledocarpaceae, Vivianaceae.

Habit and leaf form. Mostly hairy herbs, or shrubs (less often); bearing essential oils. ‘Normal’ plants, or switch-plants. Plants non-succulent (mostly), or succulent (exemplified by the xeromorphic Sarcocaulon, with fleshy stems and thorns derived from the petioles, which harden after the laminae fall). Shrubs leptocaul, or pachycaul. Mesophytic, or xerophytic. Leaves alternate (the upper, often), or opposite (the lower, usually); petiolate; non-sheathing; gland-dotted, or not gland-dotted (?); aromatic (often, via capitate glands), or without marked odour; simple, or compound; when compound palmate (usually), or pinnate (rarely). Lamina when simple, dissected; when simple palmatifid (usually), or pinnatifid (rarely); pinnately veined (rarely), or palmately veined (usually). Leaves usually stipulate. Stipules interpetiolar, or intrapetiolar (usually twinned at the base of the petiole); scaly, or leafy, or spiny. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial. Stomata present; mainly confined to one surface, or on both surfaces; anomocytic. Hairs usually present; eglandular, or eglandular and glandular; unicellular and multicellular (the glandular types with uniseriate stalks and spherical, multicellular heads). Lamina without secretory cavities. Minor leaf veins with phloem transfer cells (Erodium, Geranium), or without phloem transfer cells (Erodium, Geranium, Pelargonium).

Axial (stem, wood) anatomy. Pith usually homogeneous (of thin walled parenchyma). Cork cambium present; initially superficial (and in the bizarre Sarcocaulon, giving rise to several layers of easily detachable cork, the cells resin-filled). Nodes tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles (e.g., in Erodium and shrubby species of Pelargonium), or comprising a ring of bundles, or comprising two or more rings of bundles (often exhibiting a pericyclic ring of sclerosed tissue, the bundles in herbaceous species widely separated and often arrranged in two rings, those of inner rings sometimes inversely orientated). Medullary bundles present (the inner ring of bundles tending to be medullary , in Geraniumspp.), or absent. Secondary thickening absent, or developing from a conventional cambial ring (with a normal interfascicular cambium in shrubby species).

The wood ring porous to diffuse porous. The vessels solitary, or radially paired to in radial multiples, or clustered. The vessel end-walls simple. The vessels without vestured pits; with spiral thickening (in Balbisia), or without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres; at least sometimes including septate fibres, or without septate fibres. The fibres without spiral thickening. The parenchyma scanty paratracheal. The secondary phloem not stratified. ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (usually); when aggregated, in cymes, or in umbels. Inflorescences terminal, or axillary, or leaf-opposed; often pedunculate, usually consisting of paired flowers or umbels; with involucral bracts (commonly), or without involucral bracts. Flowers bracteolate; small, or medium-sized; regular to somewhat irregular. The floral irregularity involving the perianth and involving the androecium (Pelargonium). Flowers usually 5 merous; cyclic; tetracyclic to polycyclic. Free hypanthium absent. Hypogynous disk present (usually), or absent (Pelargonium); of separate members (alternating with C, around A).

Perianth with distinct calyx and corolla (usually), or sepaline (corolla sometimes missing); 5, or (7–)10; 2 whorled (usually), or 1 whorled; isomerous (usually), or anisomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous (sometimes basally connate, or forming a lobed tube). Calyx lobes markedly shorter than the tube to markedly longer than the tube. Calyx regular, or unequal but not bilabiate; basally appendaged (Pelargonium, where the posterior member is prolonged into a tube adnate to the peduncle), or neither appendaged nor spurred; persistent; imbricate (with valvate tips); with the median member posterior. Corolla (2–)5; 1 whorled; polypetalous; imbricate, or contorted (rarely); unequal but not bilabiate, or regular; deciduous (caducous). Petals clawed.

Androecium 5, or 10, or 15 (1, 2 or 3 times C). Androecial members branched (rarely), or unbranched; when many, maturing centripetally; all equal to markedly unequal; coherent; 1 adelphous (basally connate), or 5 adelphous (rarely, with five triandrous bundles); (1–)2(–3) whorled. The androecial bundles when bundled, opposite the corolla members. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 1–5; external to the fertile stamens, or external to the fertile stamens and in the same series as the fertile stamens (some or all of the outer whorl). Stamens 5, or 10, or 15; isomerous with the perianth, or diplostemonous (usually), or triplostemonous; alternisepalous (obdiplostemonous when more than one whorl, or in five antepetalous bundles); opposite the corolla members, or both alternating with and opposite the corolla members. Anthers dorsifixed; usually versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. Anther wall initially with one middle layer. Tapetum amoeboid, or glandular. Pollen grains aperturate, or nonaperturate; (2–)3(–15) aperturate (to ‘many); colpate, or colporate (more often), or foraminate; 3-celled (in Erodium and Pelargonium).

Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary 5 locular. Styles 1 (with an elongating, persistent column); attenuate from the ovary; apical. Stigmas 5; dry type; papillate; Group II type. Placentation axile. Ovules 1 per locule, or 2 per locule; pendulous, or ascending; usually epitropous; usually with ventral raphe; usually superposed; anatropous to campylotropous (becoming campylotropous after fertilization); bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; very ephemeral. Endosperm formation nuclear. Embryogeny onagrad, or asterad.

Fruit non-fleshy; a schizocarp. Mericarps 5 (these 1-seeded, separating acropetally from the central ‘beak’, each taking a strip from the style to acquire a usually hygroscopically active awn, sometimes dehiscent). Seeds non-endospermic; exotegmic. Cotyledons 2; folded. Embryo chlorophyllous (3/14); straight, or curved to bent. The radicle dorsal.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3 and CAM. C3 physiology recorded directly in Erodium, Monsonia, Pelargonium including P. peltatum (Krenzer et al. 1975), Sarcocaulon. CAM recorded directly in Geranium, Pelargonium peltatum (Mooney et al 1977). Anatomy non-C4 type (Erodium). Not cyanogenic. Alkaloids present (commonly), or absent. Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols present; kaempferol and quercetin (mostly, in abundance), or kaempferol, quercetin, and myricetin. Ellagic acid present (4 species, 2 genera), or absent (2 of the Geranium species and a Pelargonium). Aluminium accumulation not found. Sieve-tube plastids S-type.

Geography, cytology. Frigid zone to tropical. Cosmopolitan. X = 7–14.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Geraniales. Cronquist’s Subclass Rosidae; Geraniales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Geraniales.

Species 750. Genera 5; Geranium, Erodium, Monsonia, Pelargonium, Sarcocaulon.

General remarks. The taxonomic worth of segregate families depends on the soundness of the compiled data, in particular on the assumption that this attempted sensu stricto description does not significantly under-estimate variation.


Ring a’ring o’geraniums,
A pocketful of uranium,
Hiroshima -
All fall down
(anon? - quoted by Robert Graves, ‘The Crowning Privilege’)

Illustrations. • Le Maout and Decaisne: Geranium robertianum. • Le Maout and Decaisne: Geranium robertianum, Erodium, Monsonia. • Monsonia biflora: Thonner. • Erodium cicutarium, E. moschatum and E. maritimum: Eng. Bot. 307–309, 1864. • Erodium pelargoniiflorum: Bot. Mag. 86 (1860). • Geranium sanguineum and Geranium phaeum: Eng. Bot. 293–294, 1864. • Geranium molle: Eng. Bot. 299, 1864. • Geranium nodosum, G. sylvaticum and G. pratense: Eng. Bot. 295–297, 1864. • Geranium rotundifolium and G. dissectum: Eng. Bot. 301–302, 1864. • Geranium columbinum, G. lucidum and G. robertianum: Eng. Bot. 303–305, 1864. • Geranium spp.: pratense, robertianum, sanguineum (B. Ent. compilation, 1824–35). • Geranium, Erodium (B. Ent. compilation, 1824–35). • Geranium phaeum: B. Ent. 670. • Geranium pratense: as G. rubifolium Lindl., Bot. Reg. xxvi, 67 (1840). • Geranium striatum: Bot. Mag. 2 (1788). • Pelargonium glaucum: Bot. Mag. 2 (1788).

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: 5th March 2018.’.