Java Waterdropwort

The complex nomenclatural history reflects the taxonomic problems with these morphologically very variable, widespread plants. Leaf morphology is particularly variable, and the size and shape of the leaves of the subsp. javanica converge with subsp. rosthornii in Malaysia and adjoining areas. Outside China, some authors have a broader species concept for Oenanthe javanica, including O. benghalensis and O. linearis within it. Further work over a wide geographic area is needed to resolve the classification.

A common plant in wet places from the plains to 2000 m.

Plants 10–80 cm. Roots fibrous. Stems decumbent. Basal petioles 5–10 cm; blade oblong-ovate, 1–2-pinnate; ultimate segments ovate or rhombic-ovate, 5–50 × 5–20 mm, margins serrate. Cauline leaves gradually reduced upwards, smaller, becoming sessile on expanded sheaths. Umbels 3–5 cm across; peduncles 2–16 cm; bracts absent, or occasionally 1, linear, 3–11 mm; rays 6–16(–30), 1–3 cm, subequal or unequal; bracteoles 2–8, linear, 2–4 cm, as long as pedicels; umbellules ca. 20-flowered; pedicels 1.5–4 mm. Calyx teeth ca. 0.5 mm. Styles patent, 1.2–2 mm. Fruit subglobose or ovoid, ca. 2.5 × 2 mm; dorsal and intermediate ribs slightly corky-thickened.

Erect to decumbent, c. 1 m tall, glabrous. Stem stoloniferous, rooting at the nodes; roots fibrous. Upper leaves ternate; lower pinnate; leaflets oval to ovate; margin serrate. Umbels leaf opposed. Rays 10-20, stout. Calyx teeth dis¬tinct, linear, persistent. Pedicels 2-4 times longer than the flowers. Stylopodium conical, surrounded by the calyx teeth; styles 2 mm long. Fruit oblong, c. 2 mm long, 1 mm broad; dorsal and intermediate ridges obtuse, not prominent, lateral corky.

Throughout China [India, Indonesia, Japan, Korea, Laos, Malaysia, Myanmar, Nepal, New Guinea, Pakistan, Philippines, Russia, Thailand, Vietnam].

Distribution: Pakistan, India, S.E. Asia, China, Japan.

Grassland at forest margins, marshlands, water meadows, lakeshores, river banks, muddy stream banks, shallow water; 600–4000 m.