| Abstract: | The anatomical structure of the wood of Bretschneidera sinensis Hemsl. was studied with both light and scanning electron microscopy. The main characters of the secondary xylem are as follows: (1) The wood is diffuse porous with distinct growth ring. (2) Most vessel elements possess simple perforation plates, only a few are with scalariform perforation plates, but both of them have spiral thickenings on their secondary walls. (3) Tracheids, fiber-tracheids and libriform fibers all exist and the libriform fibers may or may not have septa. (4) Wood parenchyma is mainly of terminal distribution type. (5) Wood ray is heterogenous belonging to the Krib′s heterogenous IIB type. (6) Tylosis, resin canal and secretory cell are absent. Based on the present study and other data derived from external morphology, bark anatomy, chromosome study, palynology and embryogenetic study, the systematic position of Bretschneidera sinensis was analysed and discussed. The authors agree that the genus should be elevated to the level of a monotypic family—Bretschneideraceae, belonging to the order of Sapindales; also it is closely related to other primitive families of the same order such as Staphyleaceae, Sabiaceae and Connaraceae. |
