Polygonum oxyspermum subsp. raii, (Bab.) D. A. Webb & Chater

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 : 78

(b) Subsp. raii (Bab.) D. A. Webb & Chater , Feddes Repert. 68:188 (1963)

( P. raii Bab. , P. robertii auct.,? an Loisel.):

Annual to perennial, green or somewhat glaucous. Leaves usually elliptical, very variable in width. Perianth-segments with white or pale pink margins; nut 2-5-5- 5 mm, dark brown, slightly or considerably exceeding the perianth. 2« = 40. Shores of N. W. Europe, from N. W. France to arctic Russia; also locally in W. Mediterranean region.

P. norvegicum Sam. ex Lid , Norsk Flora 250 (1952) from Fennoscandia is considered a distinct species or subspecies by some authors but it does not, however, seem possible at present to distinguish it satisfactorily from variants occurring in S. & S. E. Europe.

The plants from the Mediterranean probably correspond to P. robertii Loisel. , Mém. Soc. Linn. Paris 6: 409 (1827), but the name is of uncertain application. They differ from those of the Atlantic coasts only in their smaller nut and a greater tendency towards a perennial habit.

The plants from the Black Sea coast (Turkey to Krym), which have been called P. mesembricum Chrtek , Preslia 32: (I960) may perhaps constitute a third subspecies, but their range of variation cannot yet be adequately assessed. They appear to be annual or biennial, with greyish-green or silvery leaves, ochreae with 6-8 veins, and white margins to the perianth. The nut is said to be generally similar to that of (b), but in some cultivated specimens can approach that of (a).