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The families of flowering plants

L. Watson and M.J. Dallwitz

Hamamelidaceae R. Br.

Including Disanthaceae (Harms) Nak., Fothergilleae (Fothergillaceae) Link, Parrotiaceae Horan.; excluding Altingiaceae, Rhodoleiaceae.

Habit and leaf form. Trees and shrubs (often with stellate indumentum); leptocaul. Mesophytic, or xerophytic. Leaves evergreen, or deciduous; alternate; spiral, or distichous; petiolate; non-sheathing; aromatic, or without marked odour; simple. Lamina dissected, or entire; often palmatifid; palmately veined, or pinnately veined; cross-venulate. Leaves stipulate. Stipules often persistent (sometimes large). Leaf development not ‘graminaceous’. Domatia occurring in the family (known from two genera); manifested as pockets.

Leaf anatomy. The leaf lamina dorsiventral. Mucilaginous epidermis present, or absent. Stomata present; paracytic. Hairs present; amost exclusively eglandular; unicellular (occasionally), or multicellular (mostly). Complex hairs commonly stellate (or tufted). Adaxial hypodermis absent. Lamina without secretory cavities (nearly always), or with secretory cavities (? - cortical secretory canals having been reported in Mytilaria). The mesophyll with sclerenchymatous idioblasts (very commonly), or without sclerenchymatous idioblasts; containing crystals. The crystals druses and solitary-prismatic. Minor leaf veins without phloem transfer cells (Disanthus, Parrotia).

Axial (stem, wood) anatomy. Secretory cavities absent. Cork cambium present; initially superficial. Nodes tri-lacunar. 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 narrow (uni-or biseriate).

The wood diffuse porous. The vessels small; solitary (commonly, exclusively), or solitary, radially paired, and in radial multiples. The vessel end-walls scalariform, or reticulately perforated and scalariform. The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids, or without tracheids; without vasicentric tracheids; with fibre tracheids (usually), or without fibre tracheids; without septate fibres. The fibres with spiral thickening, or without spiral thickening. The parenchyma apotracheal; wood not storied. Tyloses present, or absent.

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or andromonoecious, or polygamomonoecious. Pollination anemophilous, or entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in spikes (usually), or in heads, or in racemes, or in panicles. The ultimate inflorescence units racemose. Inflorescences with involucral bracts (sometimes), or without involucral bracts; pseudanthial (sometimes, with coloured involucral bracts), or not pseudanthial. Flowers bracteate; small (sometimes precocious); regular (usually); usually 4–5 merous; cyclic; tetracyclic. Free hypanthium present to absent. Hypogynous disk present (between A and G), or absent; when present, intrastaminal; when present, of separate members, or annular.

Perianth with distinct calyx and corolla, or sepaline (often), or vestigial to absent (rarely); 1 whorled, or 2 whorled; isomerous, or anisomerous. Calyx 4, or 5; 1 whorled; polysepalous, or gamosepalous; regular; imbricate (usually). Corolla when present, (2–)4, or 5; 1 whorled; gamopetalous; valvate, or with open aestivation (the petals sometimes long and coiled watchspring-like in bud); regular. Petals clawed, or sessile.

Androecium 4–5, or 10–14, or 15–32. Androecial members when numerous maturing centripetally, or maturing centrifugally; free of the perianth; free of one another; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes sometimes alternating with the fertile members. Stamens 4–32. Anthers usually basifixed; dehiscing via pores to dehiscing via short slits, or dehiscing via longitudinal slits, or dehiscing by longitudinal valves (mostly); introrse; tetrasporangiate; usually appendaged (via extension of the connective). Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate, or 4–15 aperturate; colpate, or colporate, or rugate; 2-celled.

Gynoecium 2 carpelled (usually), or 3 carpelled (rarely). The pistil 2 celled. Gynoecium apocarpous to syncarpous; semicarpous to synovarious (the carpels often free at the apex); superior to inferior. Ovary 2 locular. Gynoecium median; stylate. Styles 2 (usually, often recurved), or 3; free to partially joined; apical. Stigmas dry type; non-papillate; Group II type. Placentation axile. Ovules 1–6(–15) per locule; pendulous; ‘halfway between apotropous and epitropous’ (Endress, 1993); non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Endosperm formation nuclear.

Fruit non-fleshy; dehiscent; a capsule (with woody exocarp and horny endocarp). Capsules septicidal, or loculicidal. Seeds endospermic. Endosperm oily. Seeds winged, or wingless. Embryo well differentiated. Cotyledons 2; flat. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Sugars transported as sucrose (Parrotia), or as sugar alcohols + oligosaccharides + sucrose (Corylopsis). Not cyanogenic. Alkaloids absent (7 species). Iridoids not detected. Proanthocyanidins present, or absent; when present, cyanidin and delphinidin, or delphinidin. Flavonols present (usually), or absent; quercetin, or quercetin and myricetin, or kaempferol, quercetin, and myricetin. Ellagic acid present (Corylopsis), or absent (mostly — 6 species, 6 genera). Sieve-tube plastids S-type.

Geography, cytology. Temperate to tropical (mostly subtropical). North and South temperate to tropical.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Hamamelidales. Cronquist’s Subclass Hamamelidae; Hamamelidales. APG 3 core angiosperms; core eudicot; unplaced at Superordinal level; Order Saxifragales.

Species 80. Genera about 25; Chunia, Corylopsis, Dicoryphe, Disanthus, Distiliopsis, Distylium, Embolanthera, Eustigma, Exbucklandia, Fortunearia, Fothergilla, Hamamelis, Loropetalum, Maingaya, Matudaea, Molinadendron, Mytilaria, Neostrearia, Noahdendron, Ostrearia, Parrotia, Parrotiopsis, Sinowilsonia, Sycopsis, Tetrathyrium, Trichocladus.

Illustrations. • Technical details: Corylopsis (Lindley). • Corylopsis glandulifera: Hook. Ic. Pl. 29 (1906). • Corylopsis himalayana: Bot. Mag. 110 (1884). • Corylopsis pauciflora: Bot. Mag. 126 (1900). • Exbucklandia populnea, as Bucklandia: Bot. Mag. 106 (1880). • Technical details: Hamamelis. • Loropetalum subcordatum: Hook. Ic. Pl. 15 (1883). • Trichocladus grandiflorus: Hook Ic. Pl. 15 (1885).

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: 30th September 2017.’.