Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Stamens 4–5; pet often long-persistent; ovary conic; placentas basal or nearly so; styles 3–4, short-clavate or obovate; fr conic, separating completely into 3 or 4 valves; deciduous shrubs or trees with small, scale-like, often imbricate lvs and numerous small fls in racemes or spikes borne on the old wood or aggregated into a terminal panicle. 50, Old World. Two spp. occasionally escape from cult. in our range, but are scarcely members of our established flora. T. parviflora DC. has 4-merous fls, with the filaments seated on the 4 lobes of the disk. T. chinensis Lour. has 5-merous fls, with the filaments arising from (or just outside) the sinuses of the 5-lobed disk (the disk lobes often emarginate). (T. ramosissima; T. pentandra, an illegitimate name)