四蕊狐尾藻 si rui hu wei zao

Plants monoecious. Stem few branched, to 200 cm. Submerged leaves 5-whorled, pectinate, ovate to oblong in outline, ca. 4 × 10 cm; segments in 10-20 pairs, filiform, to 1.3 cm; emergent leaves narrower. Inflorescence a terminal spike of 5-whorled flowers; bracts entire at margin; bracteoles digitate at margin. Flowers 4-merous. Sepals triangular, ca. 1 mm, margin entire or finely serrate. Petals spatulate, ca. 1 mm, caducous. Fruit 4-loculed, subcylindric, ca. 3 mm; mericarps sparsely tuberculate to smooth. Fl. and fr. Mar-Sep.

Shallow waters; near sea level to 200 m. Hainan [India, Malaysia, Thailand, Vietnam].