Blackstonia perfoliata subsp. perfoliata

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 : 56

(a) Subsp. perfoliata ;

Usually robust. Upper cauline leaves triangular, not or scarcely narrowed towards the base. Flowers 8-15 mm, 6- to 8-merous. Calyx-lobes linear, 1 -veined. 2« = 40. Throughout most of the range of the species, but rare in the south.