Rediscovery of Dionysia bachtiarica (Primulaceae) in kuh-e kallar after 119 years

Botanical exploration in 2022 in the province of Chaharmahal and Bakhtiari, resulted in the collection of Dionysia bachtiarica, a narrow endemic species first collected in 1902 and described in 1905. This species has not been seen since 1903. Some morphological features were incompletely recorded, absent, or untrustworthy in earlier descriptions, due to limited herbarium material. In this study, new morphological data are provided based on analysis of live flowering and fruiting material, illustrated with photographs of the plant and its habitat, as well as line drawings. A full description of the species, its ecology, and phenology, as well as a key to all purple-flowered species in the Zagros Mountains, are provided. The possible relations of this enigmatic species are discussed. Due to its extremely limited known area of occurrence and a small number of individuals, it is considered to be Critically Endangered.