Glossary of Plant Systematics (1st ed.) by Simpson (2006)
- The ancestral type of tracheary element that is imperforate, in which water and mineral nutrients flow between adjacent cells through the primary cell walls at pit-pairs.
Glossary of "Life (9th ed.)" by Sadava et al. (2011)
- A type of tracheary element found in the xylem of nearly all vascular plants, characterized by tapering ends and walls that are pitted but not perforated. (Contrast with vessel element.)
Glossary of "The Evolution of Plants (2nd ed.)" by Willis & McElwain (2014)
- Elongated water-conducting cells.
- 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.
- Simpson, M. G. 2006. Plant Systematics. -xi + 590 pp. Elsevier Academic Press, Oxford.
- Willis, K. J. & McElwain, J. C. 2014. The Evolution of Plants, 2nd ed. -ix + 398 pp. Oxford University Press, Oxford.