Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- The meristematic tissue that generates secondary xylem and phloem (wood and inner bark); occurs in woody plants.
Glossary of Plant Systematics (1st ed.) by Simpson (2006)
- A cylindrical sheath of cells that undergoes primarily tangential divisions, producing secondary xylem (wood) to the inside and secondary phloem (inner bark) to the outside.
Glossary of "Life (9th ed.)" by Sadava et al. (2011)
- In plants, a lateral meristem that gives rise to secondary xylem and phloem.
- Graham, L. E., Graham, J. M. & Wilcox, L. W. 2003. Plant Biology. -xxxv + 497 pp. Pearson Education, Inc., Upper Saddle River.
- Simpson, M. G. 2006. Plant Systematics. -xi + 590 pp. Elsevier Academic Press, Oxford.
- Sadava, D., Hillis, D. M., Heller, H. C. & Berenbaum, M. R. 2011. Life: The Science of Biology, 9th ed. -xliv + 1266 pp. Sinauer Associates, Inc., Sunderland.