114 Vs HCaBza Borrador_A ABto Col ama 4a5f5s

those of Lycopodium. An exarch protostele was present at the base of the trunk, but above it became solenostele (see Fig. 7.28). A vascular cambium evidently arose at an early stage, but above it added only a narrow zone of secondary xylem to the primary. The formation of secondary phloem is doubtful. Additional secondary activity occurred in the outer cortex, resulting in a hard sclerotic periderm which undoubtedly provided the principal mechanical to the trunk. The inner cortex contained elongated cells, a so- called “secret 2f12d