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The families of flowering plants

L. Watson and M.J. Dallwitz

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. The leaf lamina dorsiventral. Stomata present; mainly confined to one surface (abaxial); anomocytic. The mesophyll containing crystals. The crystals druses, or solitary-prismatic. Minor leaf veins without phloem transfer cells.

Axial (stem, wood) anatomy. Young stems with solid internodes. Pith homogeneous (comprising thick-walled cells which are smaller around the periphery). Cork cambium present; initially deep-seated to initially superficial (in the outer cortex). Nodes tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels very small (and angular); solitary, radially paired, and in radial multiples. The vessel end-walls scalariform (with numerous cross bars). The vessels with spiral thickening. The axial xylem with fibre tracheids; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal. ‘Included’ phloem absent. The wood not storied. Tyloses present, or absent.

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, phytochemistry. Not cyanogenic. Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid present. Aluminium accumulation not found. Sieve-tube plastids S-type.

Geography, cytology. Holarctic. Temperate. Eastern Asia. 2n = 28.

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

Species 1 (Cercidiphyllum japonicum). Genera 1; only genus, Cercidiphyllum.

Economic uses, etc. An important Asian timber, and widely grown elsewhere as an ornamental.

Illustrations. • Cercidiphyllum japonicum (Hutchinson).

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: 5th March 2018.’.