Nigella arvensis subsp. arvensis

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1964, Flora Europaea - Volume 1. Lycopodiaceae to Platanaceae, Cambridge University Press : 209

(a) Subsp. arvensis :

Leaves green, soft, cauline not crowded to form an involucre below the flower. Follicles not transversely rugose. Throughout the range o f the species.