Fig. 3

Occurrence of vessel elements in secondary xylem. a–c Light micrographs of wood sections from transverse, radial, and tangential sections of T. sinense, respectively. In the transverse sections, radial files of the peculiar cells are indicated by the arrows. Bar = 200 and 50 μm in a, c, and b. d Scanning electron micrographs of the radial surface in T. sinense, showing scalariform pits. Scale bar = 20 μm. e Scalariform pits with fibrillar mesh membrane remnants. Scale bar = 10 μm. f–i Three-dimensional (3D) images of X-ray computed microtomography (microCT). f Original rendering of the 3D microCT image in T. sinense. g–i Images of radial (y–z) and tangential (x–y) sections of 3D microCT image at 3 different longitudinal positions of transverse sections (x–z). Arrows in g indicate the peculiar cells appearing in the tangential section. j Enlargement of h showing the short and fusiform peculiar cells. Light green dotted lines represent these peculiar cells. Scale bars are indicated by axis labels in f–h and 200 μm in j