Including Erodiaceae Horan., Rostraceae DulacExcluding Biebersteiniaceae, Dirachmaceae, Hypseocharitaceae, Ledocarpaceae, Vivianaceae
Habit and leaf form. Herbs (usually), or shrubs; bearing essential oils. ‘Normal’ plants, or switch-plants. Plants succulent (rarely — e.g. Sarcocaulon, with fleshy stems), or non-succulent. 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. Leaves without a persistent basal meristem.
Leaf anatomy. Stomata present; mainly confined to one surface, or on both surfaces; anomocytic. Hairs usually present; eglandular; multicellular.
Lamina dorsiventral, or isobilateral; without secretory cavities. Minor leaf veins with phloem transfer cells (Erodium, Geranium), or without phloem transfer cells (Erodium, Geranium, Pelargonium).
Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Secondary thickening absent, or developing from a conventional cambial ring. Xylem with libriform fibres. Vessel end-walls simple. Wood parenchyma scanty paratracheal. Sieve-tube plastids S-type.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (usually); 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, biochemistry. Not cyanogenic. Alkaloids present (commonly), or absent. Iridoids not detected. 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). Arbutin absent. Saponins/sapogenins absent. Aluminium accumulation not found. 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).
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 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Geraniales.
Species 750. Genera 5; Geranium, Erodium, Monsonia, Pelargonium, Sarcocaulon.
• Technical details: Geranium robertianum.
• Technical details (Geranium robertianum, Erodium, Monsonia).
• Technical details: Monsonia (Thonner).
• Erodium cicutarium, E. moschatum and E. maritimum: Eng. Bot. 307–309, 1864.
• 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).
• Geranium, Erodium (B. Ent. compilation).
• 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.
Ring a’ring o’geraniums,
A pocketful of uranium,
All fall down
(anon? - quoted by Robert Graves, ‘The Crowning Privilege’)