In the botanical history of the genus Streptocarpus, the botanical research of Dr Bill Burtt from the Royal Botanical Garden Edinburgh on Streptocarpus starting around 1945 needs special mention. Thanks to his activity Royal Botanical Garden Edinburgh probably currently holds the biggest living collection of Streptocarpus in the world. Burtt started working on African Streptocarpus after his description of the Saintpaulia species. During the 1950’s and 1960’s the botanical exploration of Madagascar by Professor Henri Humbert led to his description of 20 Madagascan species of Streptocarpus (Humbert, 1967), four Madagascan Streptocarpus species were described by other authors and Burtt described 17 further Madagascan species based on the collections of Humbert and his French colleagues. Two Didymocarpus species and one species of Colpogyne, also members of the Gesneriaceae, were also described from there. Together these species were described in the Flora of Madagascar which was posthumously written for Humbert by Burtt and Monique Keraudren-Aymonin (Humbert, 1971). The description of the Madagascan species astounded botanists because of their diversity of growth and flower forms. Burtt’s previous work on Saintpaulia allowed him to critically compare Saintpaulia with the Saintpaulia-like species from Madagascar. They possessed typical twisted seed capsules whilst the African Saintpaulia species did not, but their tight leaf rosette growth form was almost identical.
In the 1960’s Burtt worked on Streptocarpus in South Africa with Professor Olive Hilliard, curator of the Bews herbarium at the University of Natal (now KwaZulu Natal) which led to the book on the genus by Hilliard & Burtt (1971) which describes 132 species in the genus which included the Madagascan species. This remains the most important monograph on the genus, a must-have book for the Streptocarpus fanatic. Hilliard subsequently joined Burtt at the Royal Botanical Garden Edinburgh and together they described many more species in the genus.
Streptocarpus research was conducted, and species descriptions were made by Professor Trevor Edwards, curator of the Bews herbarium at the University of KwaZulu Natal, in the period from around 1990 to 2010. However, the Royal Botanical Garden Edinburgh currently leads Streptocarpus research with a team headed by Dr Michael Moeller, cytologist, DNA sequencing and phylogenetics expert, and his colleagues Elspeth Haston, Mark Hughes, Kwitong Jong, Kanae Nishii and many students that studied there. My contribution has been to describe a few new species, and to conduct research with Michael Moeller, Mark Hughes and Trevor Edwards on the phylogenetic relationships within the genus with my students Margaret de Villiers, Thea Hanekom and Wiets Roos, and to thereby contribute to the sectional revision of the genus with Nishii and Moeller.
The current number of described Streptocarpus species according to the International Plant Names Index (IPNI) is 185 but this number is set to rise as species often have tiny ranges as in Pondoland (Grieve et al., 2024). Remote areas of Africa will undoubtedly hold more species.