Lemos R. C. C. D., Melo-de-Pinna G. F. D. A., Morpho-anatomical variations during stem development in some epiphytic Cactaceae, The Journal of the Torrey Botanical Society, 2011, 138(1):16-25, doi: 10.3159/10-RA-054.1
Comparative anatomical study of older and younger stem segments in four epiphytic cactus species. It describes developmental variation in the epidermis, pericycle, secondary xylem and pith. Unlignified parenchyma occurs in bands in Hatiora wood and in small groups in the examined Rhipsalis species. The authors emphasize the importance of segment age and position when interpreting anatomical characters.