Cercidiphyllaceae Van Tiegh.
Habit and leaf form. Trees (with long- and short-shoots). Leaves deciduous; alternate (on the short-shoots), or opposite (on the long-shoots); simple. Lamina pinnipalmately or palmately veined; cross-venulate; mostly more or less cordate. Leaves stipulate. Stipules intrapetiolar (adnate to the petiole); caducous. Lamina margins crenate to serrate.
Leaf anatomy. Stomata present; anomocytic.
The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses, or solitary-prismatic. Minor leaf veins without phloem transfer cells.
Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with vessels. Vessel end-walls scalariform (with numerous cross bars). Primary medullary rays narrow. Wood parenchyma apotracheal. Sieve-tube plastids S-type.
Reproductive type, pollination. Plants dioecious. Floral nectaries absent. Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; condensed in racemes (short, male), or in heads (female). Inflorescences terminal (on the short shoots, appearing with or before the leaves); those of female flowers with involucral bracts (these sepal-like), or without involucral bracts; pseudanthial (female, under the current interpretation), or not pseudanthial (male). Flowers bracteate (in female infloresences, and the lower flowers of male inflorescences). Bracts not calyptrate. Hypogynous disk absent.
Perianth absent (unless the female infloresence as described here (cf. Cronquist) is interpreted as a flower (cf. Hutchinson)).
Androecium 8–13. Androecial members free of one another. Androecium exclusively of fertile stamens. Stamens 8–13; long filantherous (with elongate filament and anther). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; latrorse; tetrasporangiate; appendaged. The anther appendages apical (representing the shortly prolonged connective). Microsporogenesis simultaneous. Tapetum glandular. Pollen grains aperturate; 3 aperturate; weakly colpate; 2-celled.
Gynoecium 1 carpelled. The pistil 1 celled. Gynoecium monomerous; of one carpel; superior. Carpel stylate; apically stigmatic (narrowing into a slender style with a decurrent, two ridged stigma); 30–100 ovuled (‘many’). Placentation marginal (laminar-lateral, the suture abaxial, facing the subtending bract). Ovary subsessile to stipitate. Ovules pendulous; in two rows; anatropous; 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; small. Synergids pear-shaped. Endosperm formation cellular. Embryogeny caryophyllad.
Fruit non-fleshy. The fruiting carpel dehiscent; a follicle. Gynoecia of adjoining flowers combining to form a multiple fruit (each of these comprising a cluster of follicles). Seeds copiously endospermic. Endosperm oily. Seeds winged (and flattened, nearly square). Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous (1/1).
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid present. Arbutin absent. Saponins/sapogenins absent. Aluminium accumulation not found.
Geography, cytology. Holarctic. Temperate. Eastern Asia. 2n = 28.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Trochodendrales. Cronquist’s Subclass Hamamelidae; Hamamelidales. APG 3 core angiosperms; core eudicot; unplaced at Superordinal level; Order Saxifragales.
Species 1. Genera 1; only genus, Cercidiphyllum.
Economic uses, etc. An important Asian timber, and widely grown elsewhere as an ornamental.