Fig. 1.

Scanning electron microscopy images of a bordered pit with a torus–margo pit membrane between adjacent tracheids in wood of C. columellaris (Left) and C. rhomboidea (Right). Clear differences in the torus–aperture ratio can be seen, which result from a difference in aperture dimensions (A, blue area), while the torus (T, yellow) and margo (M) sizes are more or less similar. Functional implications associated with torus overlap are summarized with respect to embolism resistance, hydraulic efficiency, growth rate, and longevity.