Rorippa microphylla (Boenn. ex Rchb.) Hylander
one rowed watercress
Perennial stoloniferous herb. Stems trailing, glabrous, up to 1 m long. Lvs glabrous, all similar but becoming smaller near infl., pinnate, petiolate, 2-10-(25) × 1-5 cm; basal auricles very small; leaflets rounded, ovate; margins entire or sinuate. Pedicels glabrous, slender, erecto-patent, spreading to deflexed at fruiting, (8)-12-20-(30) mm long. Sepals 2.5-3.5 × 1 mm. Petals white, (4)-5-6 × 1.5-2.5 mm. Silique glabrous, narrow-oblong to linear, curved, (10)-15-25-(30) × c. 1.5 mm; valves with distinct midrib at least below; style c. 1 mm long. Seeds in ± 1 row per locule, brown, c. 1 mm long, reticulate with 100-150 polygonal depressions per face.
N.; S.; St.: throughout, but commonest in S.
Europe 1954
Streams, ditches and drains.
This sp. and R. nasturtium-aquaticum are very similar but most reliably distinguished by the surfaces of their seeds. R. microphylla tends to have larger fls, longer pedicels, and narrower siliques than R. nasturtium-aquaticum. R. microphylla is often treated in the genus Nasturtium as N. microphyllum Reichb.
