Gustav Mann (1836-1916) was born in Hanover in present day Germany, and became a gardener at the Royal Botanic Gardens, Kew, in 1859. He was soon recruited by the Director, William Hooker , to replace Barter as botanist on the ill-fated Niger Expedition, then exploring the reaches of this major river in West Africa under the leadership of Captain Baikie.
Attached to the British Navy, Mann arrived at the island of Fernando Po in the Gulf of Guinea after short stops in the Canary Islands and in Sierra Leone. Fernando Po was a base for the anti-slavery patrols of the British Navy at that time. While waiting for news of, and logistical opportunites to join, the Niger Expedition, Mann occupied himself by collecting specimens from Fernando Po, and after several attempts, reached the highest summit of the volcanic peak that forms the island. He regularly sent back consignments of live and dried specimens via naval ships to Kew, and letters reporting his progress to Hooker.
When eventually news arrived in Fernando Po that Barter had died and that the Niger expedition had had difficulties, it was decided that instead of travelling up the Niger, Mann should continue his collecting in the Gulf of Guinea. He remained based in Fernando Po , making forays with naval ships to locations such as Calabar (in present day Nigeria), Victoria (Cameroon), Kongui River (Gabon and Equatorial Guinea-Rio Muni), and the islands of Principé , Saõ Tomé and Annobon. His visits to Mt. Cameroon came to wider scientific attention when they became the basis for scientific papers delivered by Hooker. They also became known to a wider public due to the writings of the explorer Richard Burton, who joined Mann's third visit to Mt. Cameroon, and his expedition to the summit.
During his stay in West Africa, Mann collected thousands of very high quality specimens despite perilous conditions. Mann's letters to Hooker record the frequent deaths from diseases of other Europeans in West Africa, not for nothing then known as "White Man's Grave". Several of Mann's letters to Hooker note that he suffered from fever and the effects are visible in the calligraphy. However Mann was clearly inspired by Hooker's naming for him some of the many new species found amongst his collections.
After returning from West Africa, Gustav Mann joined the Indian Forest Service, serving for example at the tea plantations at Darjeeling. He continued to collect some specimens, particularly ferns, but not as prodigiously as in his African years. He retired in 1891 to live in Munich.
Mann's work laid firm foundations for our botanical knowledge of the Gulf of Guinea. His were the most comprehensive collections from the area for many decades, and the first for countries such as Cameroon. He is commemorated by 349 species names and several genera, Manniella Hook. f. and Manniophtyon Muell. Arg. still being maintained today.
Martin Cheek, RBG, Kew