The families of flowering plants

L. Watson and M.J. Dallwitz

Eucommiaceae Van Tiegh.

Habit and leaf form. Trees; laticiferous. Leaves deciduous; alternate; petiolate; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins serrate, or dentate.

General anatomy. Plants with laticifers (articulated, in the phloem and cortex). The laticifers in leaves and in stems.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; mainly confined to one surface (abaxial); anomocytic.

Axial (stem, wood) anatomy. Young stems with solid internodes. Pith more or less homogeneous (the peripheral cells being thicker walled). Cork cambium present; initially superficial. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Secondary thickening developing from a conventional cambial ring.

The wood semi-ring porous. The vessels very to extremely small; solitary and radially paired (but mostly solitary). The vessel end-walls oblique; simple. The vessels with spiral thickening. The axial xylem with tracheids. The parenchyma apotracheal; wood not storied. Tyloses present (rare), or absent.

Reproductive type, pollination. Plants dioecious. Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. Inflorescences intercalary; consisting of shortly pedicellate flowers solitary in the axils of bracts, these crowded at the bases of distally leafy shoots (cf. Euptelea). Flowers bracteate; ebracteolate; small; regular. Hypogynous disk absent.

Perianth absent.

Androecium in the male flowers, (5–)6–10(–12). Androecial members free of one another. Androecium exclusively of fertile stamens. Stamens (5–)6–10(–12); very shortly filantherous. Anthers linear basifixed; non-versatile; dehiscing via longitudinal slits; tetrasporangiate; appendaged. The anther appendages apical (by apical prolongation of the connective). Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer, or initially with more than one middle layer. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate (with poorly developed pores); 2-celled.

Gynoecium 2 carpelled. The pistil 1 celled. Gynoecium syncarpous (but pseudomonomerous); synstylovarious; superior. Ovary 1 locular (by abortion); sessile. Gynoecium very shortly stylate (within the V-shaped ovary apex). Styles 1; shorter than the ovary (very short). Stigmas 2 (unequal). Placentation apical. Ovules in the single cavity 2; pendulous; apotropous; with dorsal raphe; collateral; anatropous; unitegmic; weakly crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating. Synergids pear-shaped. Endosperm formation cellular. Embryogeny solanad.

Fruit non-fleshy; indehiscent; a samara (somewhat elm-like); 1 seeded. Seeds endospermic. Embryo well differentiated (large). Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Not cyanogenic. Alkaloids absent (2 species). Verbascosides not detected. Arbutin absent. Iridoids detected (aucubin); ‘Route II’ type. Saponins/sapogenins present. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent. Sieve-tube plastids S-type.

Geography, cytology. Holarctic. Temperate. China. 2n = 34.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Hamamelidae; Eucommiales. APG III core angiosperms; core eudicot; Superorder Asteranae; lamiid. APG IV Order Garryales.

Species 1 (Eucommia ulmoides). Genera 1; only genus, Eucommia.

Illustrations. • Eucommia ulmoides (Hutchinson). • Eucommia ulmoides, fruiting: Hook. Ic. Pl. 20 (1891). • Eucommia ulmoides, flowering: Hook. Ic. Pl. 24 (1895).

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: 15th April 2018.’.