Abstract
It is demonstrated that the name Cynanchum rossicum was invalidly published by Kleopow (1929) as a provisional name. In the same article he validly published C. meoticum as “Cynanchum (Vincetoxicum) meoticum”, probably with an intention to create a corresponding alternative name in Vincetoxicum. However, our analysis of the protologue demonstrates that, regardless of Kleopow’s intentions, he did not validly publish any alternative names in Vincetoxicum. After considering publications in which the name Cynanchum rossicum (or Vincetoxicum rossicum) was accepted, we conclude that C. rossicum was validated (probably inadvertently) in Index Kewensis Supplement 8 (Hill 1933). Consequently, the combination V. rossicum made by Barbaricz in 1950 through indirect reference should be cited with the authorship “(Kleopow) Barbar.” However, if validations of names in Index Kewensis supplements starting from Supplement 4 are effectively excluded, following the proposal by Sennikov et al. (2015), then under possible acceptance of that proposal at the XIX International Botanical Congress in 2017 the name V. rossicum will be attributed to Barbaricz, and C. rossicum will become illegitimate (because of its validation in 1941 with an earlier binomial V. schmalhausenii cited in synonymy). General aspects of uncertainties present in the current ICN regarding the conditions of valid publication of names are discussed, especially provisions covering alternative names and indirect reference.