Ceratophyllum demersum subsp. platyacanthum, (Cham.) Nyman

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 : 206

(b) Subsp. platyacanthum (Cham.) Nyman , Consp. 251 (1879)

(C. platyacanthum Cham.): Nut surrounded by a broad wing between the bases of the spines. Basal spines flattened, directed laterally. E. C. Europe, from Germany to Ukraine.

Plants generally similar to C. demersum , but with 5 spines on the nut (the two extra spines arising from near or slightly above the centre of each face and projecting laterally), have been recorded from time to time from various parts of Europe. In C. pentacanthum Haynald , Magyar Növ. Lapok 5: 109 (1881), described originally from Kalocsa (Hungary) and since recorded for W. France (Charente Maritime), the nut in other respects resembles that of subsp. (b); but in C. komarovii Kuzen. in Komarov, Fl. URSS 7: 719 (1937), recorded from Pavlovsk, near Leningrad, and from the Rostov region, it is closer to that of subsp. (a). The fact that two out of four records for these 5- spined plants are from ornamental ponds suggests that they may be introduced from outside Europe; and C. komarovii is, indeed, scarcely distinguishable from C. oryzetorum Komarov , Bull. Jard. Bot. URSS 30: 200 (1931) from E. Asia.