An annotated checklist and lectotypification of Ostryopsis Decne. (Betulaceae), with notes on the numbering system in the collections of P.J.M. Delavay

Here, we present an annotated checklist of the hazel-hornbeams, Ostryopsis (Betulaceae), an endemic genus from China with three species. The best character for species determination is found to be the indument on the lower leaf lamina, while the infructescence shape may be misleading. A lectotype is designated for O. davidiana and O. nobilis. The name Ostryopsis davidiana var. cinerascens, which is commonly placed to either species, turned out to be a heterotypic synonym of the lately described O. intermedia. In the course of this work, we noticed that collections by P.J.M. Delavay contain three different numbering systems, which may be of significance for type identification, especially for names by A.R. Franchet based on Delavay’s collections.