The families of flowering plants.                                                                                                                                                                

Hamamelidaceae R. Br.

                        

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IncludingDisanthaceae (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; 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). Leaves without a persistent basal meristem. Domatia occurring in the family (two genera); manifested as pockets.

Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata present; paracytic. Hairs present; eglandular; unicellular (occasionally), or multicellular (mostly). Complex hairs commonly stellate (or tufted).

Lamina dorsiventral. The mesophyll with sclerencymatous idioblasts (very commonly), or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Discanthus, Parrotia).

Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Primary vascular tissue in a cylinder, without separate bundles. Secondary thickening developing from a conventional cambial ring. Xylem with tracheids, or without tracheids; with fibre tracheids, or without fibre tracheids; with vessels. Vessel end-walls scalariform, or scalariform and reticulately perforated. Wood parenchyma apotracheal. Sieve-tube plastids S-type.

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 unit 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.

Perianthwith 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 unbranched; 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. Anthersusually 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, biochemistry. 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). Sugars transported as sucrose (Parrotia), or as sugar alcohols + oligosaccharides + sucrose (Corylopsis).

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.

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