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

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.