Tetracentron is the only genus of its family, and itself contains a single species. The family is a very ancient one, most closely allied to the Trochodendraceae, also consisting of a single genus and species (see Trochodendron). Although unalike in foliage and inflorescence, the two families have several essential characters in common, one of the most remarkable being the structure of the water-conducting tissues (xylem), which are made up, not of vessels, as in most flowering plants, but of tracheids, resembling those of the conifers but rather more primitive in form. For the foliage of Tetracentron, see below. The flowers are grouped in clusters of four on pendulous spikes and are bisexual. Sepals four, imbricated. Petals none. Stamens four. Ovary superior, composed of four united carpels. Styles four, with a minute stigma, at first terminal and erect but becoming recurved and then apparently borne at the base of the ovary. Fruit a loculicidal capsule, containing a few oily seeds.
See further in: Smith, A. C., ‘A taxonomic review of Trochodendron and Tetracentron’, Journ. Arn. Arb., Vol. 26 (1945), pp. 123-42; and Bailey, I. W., and Nast, C. G., ‘Morphology and relationships of Trochodendron and Tetracentron’, ibid., pp. 143-54 and 267-76; Takhtajan, A., Flowering Plants. Origin and Dispersal (1969), translated from the Russian by C. Jeffrey, pp. 52, 94.