Majeed S., Zafar M., Ahmad M., Kilic O., Sultana S., Raza J., Yaseen G., Gul H., Mir S., Lubna, Jabeen M., Pollen morphological investigations of family Cactaceae and its taxonomic implication by light microscopy and scanning electron microscopy, Microscopy Research and Technique, 2020, 83(7):767-777, doi: 10.1002/jemt.23467
A comparison of pollen morphology in eight cactus species under light and scanning microscopes. Thelocactus setispinus material from Pakistan has three apertural furrows and a granular, perforated exine surface.