R. Douglas Stone,¹ Martin W. Callmanderhttps://orcid.org/0000-0003-3641-112X<sup>2

1</sup>Addresses of the authors: RDS: School of Biological and Conservation Sciences, University of KwaZulu-Natal, Pietermaritzburg campus, Private Bag X01, Scottsville 3209, Republic of South Africa. Email: stonerd@ukzn.ac.za
²MWC: Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri, 63166-0299, U.S.A. and Conservatoire et Jardin botaniques de la Ville de Genève, ch. de l'Impératrice 1, CP 60, 1292 Chambésy, Switzerland.