Every procambial strand was mapped in the apical six disks of insertion comprising the shoot tip of Symplocarpus. Detection of longitudinally discontinuous procambia confirmed that the procambial leaf traces were originally isolated in this monocotyledonous shoot. The initially separate procambia of a nascent leaf trace became linked with a leaf as its leaf trace by further procambial differentiation among the procambial segments and the leaf to be served. The procambial components of the major leaf traces were formed by a succession of five waves within each of the superposed disks of insertion. Space for the additional procambia in the successive waves was made by the expansion growth of each disk. Waves 1–4 made the procambial components of the major leaf traces near the center of the disk, but wave 5 caused the lower end of a major trace to become centrifugal. The first intermediate leaf traces began after the major traces, since only waves 3–5 were involved. The mantle of the meristematic cap was the...