Garralla S., Cuadrado G. A., Pollen morphology of Austrocylindropuntia Backeb, Maihueniopsis Speg., Opuntia Mill. and Tephrocactus Lem. (Cactaceae, Opuntioideae) of Argentina, Review of Palaeobotany and Palynology, 2007, 146(1–4):1-17, doi: 10.1016/j.revpalbo.2007.01.002
The study compares pollen under light and scanning microscopy using documented herbarium specimens. It examines exine ornamentation in plants described as Tunilla corrugata and Opuntia soehrensii, now associated with Airampoa corrugata and A. ayrampo respectively.