The families of flowering plants

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L. Watson and M. J. Dallwitz

Portulacaceae Juss.

Including Metabletaceae Dulac, Lewisieae (Lewisiaceae) Hook. & Arn., Montiaceae Dum., Spaetalumeae Wyeth & Nuttall, Talinaceae Doweld; excluding Hectorellaceae.

Habit and leaf form. Shrubs and herbs (commonly mucilaginous in leaves and stems). ‘Normal’ plants. Plants succulent (often), or non-succulent. Helophytic to xerophytic. Leaves alternate, or opposite; when alternate, spiral; fleshy (often), or ‘herbaceous’; petiolate to sessile; non-sheathing; simple. Lamina entire; linear, or lanceolate, or oblanceolate, or ovate, or obovate; pinnately veined, or one-veined; cross-venulate. Leaves stipulate, or exstipulate (Claytonia). Stipules intrapetiolar; scaly (or sometimes, as in Portulaca, represented by axillary hairs). Lamina margins entire. Leaf development not ‘graminaceous’.

General anatomy. Plants with ‘crystal sand’ (Calandrinia), or without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Stomata present; on both surfaces (usually), or mainly confined to one surface; anomocytic, or paracytic. Hairs present (glandular and/or eglandular, diverse in form: see illustration). Adaxial hypodermis present (rarely), or absent. Lamina usually with mucilage cells. The mesophyll usually containing mucilage cells; usually containing crystals. The crystals raphides, or druses, or solitary-prismatic. Minor leaf veins without phloem transfer cells (Calandrina, Lewisia, Montia).

Axial (stem, wood) anatomy. Nodes unilacunar. Primary vascular tissues comprising a ring of bundles (usually), or in a cylinder, without separate bundles; at least usually collateral. Internal phloem dubiously present (e.g. in Montia), or absent. Medullary bundles absent. Secondary thickening absent, or developing from a conventional cambial ring. Primary medullary rays wide, or narrow.

The wood diffuse porous. The vessels small; solitary, or radially paired, or in radial multiples. The vessel end-walls simple. The vessels with spiral thickening, or without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres. ‘Included’ phloem absent.

Reproductive type, pollination. Unisexual flowers absent. 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 usually cymes, often dichasial or tending to cincinni. Flowers bracteolate (if the ‘sepals’ are interpreted as bracteoles); small, or medium-sized; regular to somewhat irregular; cyclic; tetracyclic. Free hypanthium present to absent. Hypogynous disk present.

Perianth with distinct calyx and corolla, or sepaline (the latter if the ostensible ‘calyx’ is interpreted as ‘bracteoles’, whereupon the ‘corolla’ becomes a petaloid calyx); 7; 2–3 whorled; anisomerous. Calyx 2; 1–2 whorled; polysepalous, or gamosepalous (the members sometimes united basally); persistent; imbricate (the upper member overlapped). Corolla if not interpreted as calyx, (2–)5(–18); 1 whorled; polypetalous, or gamopetalous (sometimes basally connate). Corolla lobes markedly longer than the tube. Corolla imbricate; regular; white, or yellow, or pink, or purple (often satiny).

Androecium 5, or 10, or 4–100 (i.e. to ‘many’). Androecial members branched (bundled, when ‘many’), or unbranched; free of the perianth, or adnate (to the corolla base); free of one another, or coherent; when coherent 1 adelphous, or 2–7 adelphous (?); 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens 3, or 4, or 5, or 10, or 6–50; isomerous with the perianth, or diplostemonous to polystemonous; when 5, alternisepalous (opposite the petals). Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with one middle layer; of the ‘monocot’ type. Tapetum glandular. Pollen grains aperturate; 3–6 aperturate, or 13–30 aperturate (or more?); colpate, or foraminate, or rugate (then pantocolpate, sometimes irregularly); 3-celled (in Portulaca and Talinum).

Gynoecium (2–)3(–9) carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior, or partly inferior (Portulaca). Ovary 1 locular. Styles 1, or 3(–9); apical. Stigmas dry type; papillate; Group II type. Placentation basal, or free central. Ovules in the single cavity 2–100 (to ‘many’); anatropous to amphitropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked (and sometimes with filiform apparatus). Endosperm formation nuclear. Embryogeny caryophyllad, or solanad.

Fruit non-fleshy; dehiscent (usually), or indehiscent; a capsule, or capsular-indehiscent. Capsules circumscissile, or valvular. Fruit elastically dehiscent (sometimes), or passively dehiscent. Seeds non-endospermic. Perisperm present. Seeds with starch. Embryo well differentiated. Cotyledons 2(–4). Embryo achlorophyllous (2 species of Portulaca); curved. The radicle dorsal.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C4 and CAM (and C4/CAM intermediates?). C4 physiology recorded directly in Anacampseros, Portulaca (plus with very weak CAM). CAM recorded directly in Anacampseros, Calandrinia, Ceraria, Portulacaria, Talinum. Anatomy C4 type (Portulaca, Trianthema: see illustration), or non-C4 type (Talinum). Not cyanogenic. Alkaloids absent, or absent. Iridoids not detected. Betalains present, or absent. Saponins/sapogenins present, or absent. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present, or absent; kaempferol. Ellagic acid absent (2 genera, 2 species). Plants often accumulating free oxalates. Sieve-tube plastids P-type; type III (a).

Geography, cytology. Temperate to tropical. Cosmopolitan, except for frigid zones. X = 4–42 (or more).

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales.

Species 580. Genera about 20; Amphipetalum, Anacampseros, Baitaria, Calandrinia, Calyptridium, Calyptrotheca, Ceraria, Cistanthe, Claytonia, Grahamia, Lenzia, Lewisia, Montia, Portulaca, Rumicastrum, Schreiteria, Silvaea, Talinella, Talinopsis, Talinum.

Economic uses, etc. A few cultivated ornamentals (Portulaca grandiflora, Talinum, Lewisia and Calandrina spp.), and Portulaca oleracea constitutes a potherb and salad green.

Illustrations. • Technical details (Portulaca). • Technical details: Talinum (Thonner). • Claytonia perfoliata: Eng. Bot. 260, 1864. • Montia fontana: Eng. Bot. 259, 1864. • Montia fontana (B. Ent.. • Peplis (B. Ent.). • Portulaca grandiflora var. splendens: as P. gilliesii, Bot. Reg. 1672, 1835. • Portulaca grandiflora var. thellusonii: Bot. Reg. xxvi, 31 (1840). • Talinum teretifolium: Bot. Reg. 29 (1), 1843. • Leaf hairs of Calandrinia umbellata, and leaf TS of Portulaca oleracea: Solereder, 1908.


The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using 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).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 16th May 2016. delta-intkey.com’.

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