Dr Thomas Coulter's cacti from Zimapán, Hidalgo, Mexico

Abstract

The Irish botanist Dr Thomas Coulter (1793–1843) sent a collection of living cacti, which he reckoned contained around 57 different ones, from Zimapán, Hidalgo province, Mexico, in February 1828 to Augustin Pyramus de Candolle. These plants reached Geneva by July 1828. Using Coulter's consignment, A. P. de Candolle described 63 species and varieties in the genera Cereus, Echinocactus, Mammillaria and Opuntia. Hitherto unpublished letters from Coulter to Candolle help to confirm the type locality of all Coulter's cacti as Zimapán, Hidalgo, and allow us to reconstruct the history of this important, early collection, which substantially increased European knowledge of cacti.