Notes on the nomenclature and taxonomy of Salix fragilis (Salicaceae)

We evaluated the recent replacements of Salix fragilis L. with S. euxina I.V.Belyaeva, and S. xrubens Schrank with S. xfragilis L. (S. alba L. x S. euxina). The specimens of S. euxina, identified by Belyaeva, were analyzed. The morphological characters did not coincide with those in the species description, and the ovule number was different in all specimens. This makes the application of the name S. euxina impossible and precludes the possibility of replacing S. fragilis for S. euxina. Also, the original Linnaean descriptions of S. fragilis, the related S. alba, and S. pentandra, as well as Linnaeus's herbarium specimens, were examined. Each of the three protologues describes the characteristics of the pure species as well as their hybrids: S. pentandra x S. fragilis (in the protologues of S. pentandra and S. fragilis) and S. alba x S. fragilis (in the protologue of S. alba). Our study of the morphology, geographic data, and ovule number demonstrates that the recent replacements of S. fragilis with S. euxina, and S. xrubens with S. xfragilis (S. alba x S. euxina) were erroneous. We propose continuing to use S. fragilis as the name for a glabrous crack willow and S. xrubens for its hybrid with S. alba.