Vinca difformis subsp. difformis

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1972, Flora Europaea. Volume 3. Diapensiacea to Myoporaceae, Cambridge: Cambridge University Press : 69

(a) Subsp. difformis :

Leaf-margins glabrous. Calyx-lobes glabrous or, very rarely, ciliate with a few sparse hairs. Corollalimb 30-45 mm in diameter. Almost throughout the range of the species.