Thesium pyrenaicum subsp. pyrenaicum

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 : 71

(a) Subsp. pyrenaicum :

Perianth 3-4 mm, mostly 5-lobed (rarely 4-lobed in isolated flowers); persistent perianth equalling nut. Throughout the range of the species.