The families of flowering plants.
IncludingCeltidaceae Link, Samaracaceae Dulac
Habit and leaf form. Trees and shrubs;non-laticiferous and without coloured juice; leptocaul. Mesophytic. Leaves evergreen, or deciduous; alternate; spiral, or distichous; petiolate; non-sheathing; simple. Lamina entire; pinnately veined, or palmately veined (then with three main veins— Celtidoideae); cross-venulate; oblique at the base (often), or oblique at the base, or rounded at the base. Leavesstipulate. Stipules interpetiolar, or intrapetiolar; free of one another, or concrescent; caducous. Lamina margins entire, or dentate (or lobulate). Vegetative buds scaly. Leaves without a persistent basal meristem. Domatia occurring in the family (3 genera); manifested as pockets, or hair tufts.
Leaf anatomy. Mucilaginous epidermis present. Stomata mainly confined to one surface (abaxial); anomocytic.
Lamina dorsiventral (usually), or isobilateral to centric (in some Celtis spp.). Cystoliths commonly present. The mesophyll containing mucilage cells, or not containing mucilage cells. Minor leaf veins without phloem transfer cells (Celtis, Zelkova).
Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones (occasionally), or not stratified. ‘Included’ phloem absent. Xylem with vessels. Vessel end-walls horizontal; scalariform (rarely), or simple. Vessels without vestured pits. Wood storied, or partially storied (VP); parenchyma usually essentially paratracheal. Sieve-tube plastids P-type, or S-type (then without starch); when P-type, type I (b). Pith with diaphragms, or without diaphragms.
Reproductive type, pollination. Plants hermaphrodite, or monoecious, or polygamomonoecious. Gynoecium of male flowers vestigial. Pollination entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in fascicles. The ultimate inflorescence unit cymose, or racemose. Inflorescences axillary; usually cymose clusters. Flowers small; regular, or somewhat irregular; cyclic. Free hypanthium present (or arguably so, when stamens are inserted on the perianth), or absent. Hypogynous disk absent.
Perianthsepaline; (2–)5(–9); free, or joined; 1 whorled (ostensibly), or 2 whorled (?—theoretically). Calyx (if the perianth is so interpreted (2–)5(–9); 1 whorled, or 2 whorled; polysepalous, or gamosepalous; unequal but not bilabiate, or regular; persistent; imbricate, or valvate (induplicate-valvate in Trema).
Androecium (2–)4–8(–15) (mostly equalling or twice K). Androecial members adnate (to the bottom of the perianth), or free of the perianth; free of one another; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens(2–)4–8(–15); reduced in number relative to the adjacent perianth, or isomerous with the perianth; oppositisepalous; erect in bud (nearly always), or inflexed in bud (sometimes, in Celtis). Anthers dorsifixed; dehiscing via longitudinal slits; extrorse (e.g. Celtis), or introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or decussate. Anther wall initially with more than one middle layer (2 to 4). Tapetum glandular. Pollen grains aperturate; 2–5(–6) aperturate; colpate (or rupate), or porate; 2-celled (Holoptelea), or 3-celled (Ulmus).
Gynoecium 2(–3) carpelled. Carpels reduced in number relative to the perianth.The pistil 1 celled, or 2 celled. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary 1 locular (usually, by abortion), or 2 locular. Gynoecium median; stylate, or non-stylate to stylate. Styles 1–2; free to partially joined; apical. Stigmas 1; dry type; papillate; Group II type. Placentation apical. Ovules in the single cavity 1; pendulous; non-arillate; anatropous, or campylotropous (Celtidoideae); bitegmic; tenuinucellate, or crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type, or Adoxa-type, or Drusa-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; proliferating (forming up to 10 cells, in Holoptelea), or not proliferating; ephemeral. Synergids pear-shaped. Hypostase present. Endosperm formation nuclear. Embryogeny onagrad, or solanad.
Fruit fleshy, or non-fleshy; indehiscent; a samara, or a nut, or a drupe. Seeds scantily endospermic, or non-endospermic (usually). Cotyledons 2; flat (Ulmoideae), or folded to rolled (Celtidoideae). Embryo achlorophyllous (2/5); straight (Ulmoideae), or curved (Celtidoideae). Micropyle not zigzag.
Physiology, biochemistry. Nitrogen-fixing root nodules present (Parasponia), or absent. Not cyanogenic (usually), or cyanogenic (Trema). Cynogenic constituents tyrosine-derived. Alkaloids present, or absent. Iridoids not detected. Proanthocyanidins present; cyanidin, or cyanidin and delphinidin. Flavonols present, or absent (Celtis,Trema); kaempferol and quercetin (Ulmus). Ellagic acid absent (4 species, 3 genera). Arbutin absent. Saponins/sapogenins present, or absent. Aluminium accumulation not found. Sugars transported as oligosaccharides + sucrose (predominantly, in 4 genera, but some myoinositol usually present as well). C3. C3 physiology recorded directly in Celtis, Ulmus.
Geography, cytology. Temperate to tropical. Widespread tropical and temperate. X = 10, 11, 14.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Urticales. Cronquist’s Subclass Hamamelidae; Urticales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Rosales.
Species 200. Genera 15; Ampelocera, Aphananthe, Celtis, Chaetachme,Gironniera, Hemiptelea, Holoptelea, Lozanella, Parasponia,Phyllostylon, Planera, Pteroceltis, Trema, Ulmus,Zelkova.
Economic uses, etc. Timber (especially for furniture) from Ulmus (elm), Planera (false sandalwood).