Baker M. A., Majure L. C., Cloud-Hughes M. A., Rebman J. P., ×Cylindronia, a New Nothogenus Representing the First Reported Hybrid Between Grusonia and Cylindropuntia (Cactaceae), Haseltonia, 2022, 29(1):5-15, doi: 10.2985/026.029.0102
The analysis of morphology, plastid DNA and nuclear ribosomal DNA confirms the hybrid origin of ×Cylindronia robertsii, formerly Grusonia robertsii. It identifies Grusonia invicta as the maternal parent and Cylindropuntia alcahes subsp. alcahes as the paternal parent.