The cacti of Franz Meyen from his around the world voyage 1830–1832

Summary: Dr. Franz Meyen (1804–1840), a physician and naturalist undertook a voyage around the world in the years 1830–1832 on board the Prussian vessel “Prinzess Louise”. Based on this journey he described numerous plants including four species of cacti. These species along with a fifth described later by Louis Pfeiffer based on Meyen's account are discussed and illustrated based on recent visits to the localities recorded by Meyen. Cereus fascicularis a name of uncertain application, although the type of the genus Weberbauerocereus and hence of significant nomenclatural importance, is dealt with and a theory as to its true identity proposed. A new combination in the genus Cumulopuntia is also proposed based on the long overlooked name Pereskia glomerata.