By means of serial sections and cinematographic methods the vascular system in the stems of certain Pandanaceae is analyzed, in both mature axes and developing crowns. This serves to establish the three‐dimensional basis for the bi‐ or tri‐polar vascular bundles which are apparent in single sections of stems of all species of Pandanaceae which so far have been examined. The basic “R/iap/s‐principle”, which characterizes woody monocotyledons, is here expressed in a distinctive way which can be seen as an important developmenta