28. Eucommiaceae Engler
Hardy rubber-tree Family Hardy rubber-tree Family
Michael A. Vincent
Trees, deciduous, dioecious; <latex present>. Leaves alternate, simple; stipules absent; petiole present; blade margins serrate; venation pinnate. Inflorescences unisexual, axillary, fascicles, (staminate) or flowers solitary (pistillate. Flowers unisexual; hypanthium absent; sepals 0; petals 0; nectary absent; stamens 5–12, distinct; anthers dehiscing by longitudinal slits; pistil 1, 2-carpellate; ovary superior, 1-locular; placentation apical; ovules 2 per locule, anatropous; style 0; stigmas 2. Fruits samaras. Seeds 1 per fruit.
Genus 1, species 1: introduced; Asia (c, w China); introduced and cultivated widely.
Placement of Eucommia has been controversial, with various authors allying it with Cornales, Euphorbiaceae, Hamamelidaceae, Trochodendraceae, and Ulmaceae (reviewed in M. A. Vincent 2002). Most recent DNA analyses support recognizing Eucommiaceae as a distinct family in Garryales (K. Bremer et al. 2001; D. E. Soltis et al. 2000). Fossil remains of Eucommia have been found in North America, Europe, and Asia, evidence that the genus was widespread in the Cenozoic and that its present-day distribution is relictual (V. B. Call and D. L. Dilcher 1997).
SELECTED REFERENCES Call, V. B. and D. L. Dilcher. 1997. The fossil record of Eucommia (Eucommiaceae) in North America. Amer. J. Bot. 84: 798–814. Vincent, M. A. 2002. Eucommia ulmoides (Hardy rubber-tree, Eucommiaceae) as an escape in North America. Michigan Bot. 41: 141–145. Zhang, Y. L., Wang F. H., and Chien N. F. 1988. A study on pollen morphology of Eucommia ulmoides Oliver. Acta Phytotax. Sin. 26: 367–370.