Damasonium alisma, Miller

1. D. alisma Miller View in CoL , Gard. Diet. ed. 8, no. 1 (1768)

( D. stellatum Thuill. ; inch D. polyspermum Cosson , D. constrictum Juz. ).

Floating leaves up to 8 x 3 cm, oblong or ovate-oblong, subcordate or truncate at the base, obtuse or rounded at the apex; aerial leaves in subterrestrial plants often lanceolate or linearlanceolate, cuneate at thebase. Petals c. 3 mm, white, with a yellow spot at the base. Carpels usually 6. Follicles 5-12 mm, graduallyor more or less abruptly contracted into the beak. 2« =28. W., S. & S.E.Europe,northwards to S. England. BI Br Ga Gr Hs It Lu Rs (W, E) Sa Si.

Very variable in size and robustness according to the depth of the water; dwarf plants with aerial leaves occur growing subterrestrially on mud. The number of ovules is unstable: usually there are 2 in each carpel, but carpels with 4-many ovules occur here and there over the range of the species, especially in small plants. Multiovulate plants from S.W. Europe and Sicilia have been described as D. polyspermum Cosson , Not. Pl. Crit. 47 (1849), but are not worth taxonomic recognition. The shape of the follicles depends on the number of seeds: the beak (empty upper part) of the carpel is elongated in 2-seeded plants, whereas in many-seeded plants the seeds occupy more of the follicle and the beak is relatively shorter and less well defined.