Description from Flora of China
Trees deciduous, dioecious. Sapwood and bark containing latex. Buds ovoid; scales deciduous. Leaves alternate, spirally arranged, exstipulate, petiolate; leaf blade simple, usually elliptic, sometimes somewhat ovate, obovate, or oblong, containing latex (forming strands if blade is transversely broken and pulled apart), pinnately veined, base rounded or cuneate-rounded, margin densely serrate with gland-tipped teeth, apex abruptly narrowed into an acuminate tip. Flowers axillary, borne near base of current year’s branchlets, very shortly pedicellate, without perianth, wind pollinated. Male flowers clustered; stamens 5–12, linear; filaments very short; anthers basifixed, 4-locular, dehiscing by longitudinal slits; connective slightly prolonged. Female flowers solitary: ovary stipitate, composed of 2 connate carpels, 1-locular, elongate, compressed, glabrous, apex 2-lobed; stigmas 2, decurrent, reflexed-spreading; ovules 2, collateral, anatropous, 1 aborting. Fruit an indehiscent samara, long elliptic to narrowly oblong, compressed, winged around margin; wing gradually narrowed at base into stipe, shortly 2-lobed at apex with sinus stigmatic; pericarp thinly leathery. Seed 1, linear, compressed, rounded at both ends; testa membranous; endosperm copious; embryo erect, large; cotyledons compressed, fleshy.
The taxonomic position of Eucommiaceae is controversial. It has been variously associated with Hamamelidales, Magnoliales, and Urticales, or placed in its own order, Eucommiales. Recent research suggests that it may belong to Garryales together with Garryaceae (including Aucubaceae) and, perhaps, Icacinaceae.
(Authors: Zhang Zhiyun, Zhang Hongda (Chang Hung-ta) ; Nicholas J. Turland)
Chang Hung-ta. 1979. Eucommiaceae. In: Chang Hung-ta, ed., Fl. Reipubl. Popularis Sin. 35(2): 116-118.