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Habit and leaf form. Herbs and shrubs (and sub-shrubs); bearing essential oils, or without essential oils; resinous (commonly), or not resinous (?). ‘Normal’ plants, or switch-plants. Leaves well developed, or much reduced (sometimes to scales). Mesophytic, or xerophytic (especially in sunny places on chalk or sand). Leaves opposite (usually), or whorled (sometimes), or alternate (rarely); flat, or rolled (often ‘ericoid’); ‘herbaceous’, or leathery, or membranous; petiolate to sessile; non-sheathing; aromatic, or without marked odour; simple. Lamina entire; one-veined, or pinnately veined, or palmately veined. Leaves stipulate, or exstipulate (when the leaf amplexicaul). Stipules intrapetiolar; free of one another; leafy. Lamina margins flat, or revolute.
General anatomy. Plants with silica bodies (recorded in leaves of Cistus, resembling cystoliths), or without silica bodies.
Leaf anatomy. The leaf lamina dorsiventral, or centric. Epidermis sometimes containing silica bodies (in Cistus), or without silica bodies. Mucilaginous epidermis present, or absent. Stomata present; mainly confined to one surface, or on both surfaces; anomocytic. Hairs of numerous kinds present (in the family: see illustration); eglandular and glandular; unicellular and multicellular. Unicellular hairs simple (characteristically represented by a peculiar ‘double’ form which, when mature, appears to have a second hair within its base, cf. Combretaceae). Complex hairs commonly present (apparently representing tufts of the peculiar ‘double’ type with their associated bases sunken in the epidermis), or absent; commonly peltate, or stellate, or capitate. Adaxial hypodermis absent. The mesophyll containing crystals. The crystals commonly druses. Minor leaf veins with phloem transfer cells (Helianthemum), or without phloem transfer cells (Cistus).
Axial (stem, wood) anatomy. Young stems cylindrical, or tetragonal in section; with solid internodes. Cork cambium present; initially superficial. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays when present, narrow.
The wood semi-ring porous to diffuse porous. The vessels extremely to very small; solitary, or solitary and radially paired, or in radial multiples (Hudsonia), or in tangential arcs. The vessel end-walls oblique; simple. The vessels with spiral thickening. The axial xylem with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma absent or rare. ‘Included’ phloem absent. The wood not storied. Tyloses present (but rare, save in Hudsonia), or absent.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes. The ultimate inflorescence units cymose. Inflorescences terminal, or axillary; various forms of cymes. Flowers bracteolate (the two bracteoles not to be confused with the two outer sepals, which may be smaller than the other three); medium-sized to large (showy); regular; cyclic (sometimes), or partially acyclic. Usually the androecium acyclic. Floral receptacle developing an androphore, or developing a gynophore (the stamens borne on or outside the well developed hypogynous disk). Free hypanthium absent. Hypogynous disk present; extrastaminal to intrastaminal.
Perianth with distinct calyx and corolla (ignoring cleistogamous flowers); (6–)10; 2 whorled, or 3 whorled. Calyx 3, or 5 (the two outer members often smaller and narrower); 1 whorled, or 2 whorled; polysepalous, or partially gamosepalous (the two outer members sometimes adnate to the inner members); usually persistent; with at least the three inner members contorted. Corolla 5 (usually), or 3 (in Lechea, missing from cleistogamous flowers); 1 whorled; polypetalous; contorted (nearly always, in the opposite direction to the sepals), or imbricate (in Lechea); regular; white, or yellow, or red; deciduous (usually caducous). Petals scarcely clawed, or sessile.
Androecium (3–)15–100 (usually ‘many’). Androecial members branched, or unbranched (?); when many, maturing centrifugally; free of the perianth; free of one another. Androecium exclusively of fertile stamens (usually), or including staminodes (Fumana). Staminodes of Fumana external to the fertile stamens. Stamens (3–)15–100 (usually ‘many’); isomerous with the perianth to polystemonous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer. Tapetum glandular. Pollen grains aperturate; (2–)3(–5) aperturate; colporate; 2-celled.
Gynoecium 3 carpelled, or 5–10 carpelled. Carpels reduced in number relative to the perianth to increased in number relative to the perianth. The pistil 1–10 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; superior. Ovary 1 locular (but sometimes incompletely 3–10 locular, by intrusion and fusion of the placentas, e.g. in Cistus). The ‘odd’ carpel anterior. Ovary sessile. Gynoecium non-stylate to stylate. Styles 1; apical. Stigmas 1 (usually, minute to large and capitate, or discoid and lobed), or 3; dry type; papillate; Group II type. Placentation parietal. Ovules in the single cavity 15–100 (usually ‘many’ — two to many on each placenta); funicled; ascending; non-arillate; orthotropous (usually), or anatropous (e.g. Fumana); bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped, or hooked (with filiform apparatus). Endosperm formation nuclear. Embryogeny solanad.
Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal, or valvular (opening from the top downwards). Seeds endospermic. Endosperm not oily. Seeds usually small; wingless. Seeds with starch. Embryo well differentiated. Cotyledons 2. Embryo chlorophyllous (1/1); curved (almost straight in Lechea), or bent, or coiled.
Seedling. Germination phanerocotylar.
Physiology, phytochemistry. C3. C3 physiology recorded directly in Helianthemum, Hudsonia. Anatomy non-C4 type (Helianthemum). Not cyanogenic. Alkaloids absent (5 species). Iridoids not detected. Saponins/sapogenins present, or absent. Proanthocyanidins present; cyanidin and delphinidin, or delphinidin. Flavonols present; kaempferol, quercetin, and myricetin. Ellagic acid absent (2 genera). Aluminium accumulation not found.
Geography, cytology. Holarctic and Neotropical. Temperate (mainly), sub-tropical to tropical (a few). Mostly North temperate, especially Mediterranean, but a few in Central and South America. X = 5–11.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Malvales. Cronquist’s Subclass Dilleniidae; Violales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Malvales.
Species 200. Genera 9; Atlanthemum, Cistus, (Crocanthemum), Fumana, Halimimum, Helianthemum, Hudsonia, Lechea, Therocistus, Turberaria.
Quotations.
Midst Alpine
clefts, or in rare grassy spots
Of mountain ridges, where the wild bee
dwells,
The Rock Rose with her yellow blossoms dots
Its dark and hoary
leaves
(Calder Campbell, quoted by Ann Pratt, ‘Wild Flowers’
(1857), - Helianthemum chamaecistus)
Illustrations. • Cistus heterophyllus: Thonner. • Le Maout and Decaisne: Helianthemum, Cistus. • Halimimum ocymoides: Bot. Mag. 93 (1867). • Helianthemum argyreum: Hook. Ic. Pl. 24 (1895). • Helianthemum nummularium (as H. vulgare) and H. apenninum (as H. polifolium): Eng. Bot. 168 and 169, 1864. • Helianthemum nummularium (B. Ent., 1829). • Tuberaria guttata, ssp. guttata and ssp. breweri: Eng. Bot. 165 and 166, 1864. • Cistus, Helianthemum: 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: 4th May 2024. delta-intkey.com’.
