Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- Ray parenchyma cells and ray tracheids, both produced by ray initials of the vascular cambium.
- Graham, L. E., Graham, J. M. & Wilcox, L. W. 2003. Plant Biology. -xxxv + 497 pp. Pearson Education, Inc., Upper Saddle River.