Myriophyllum callitrichoides Orchard

Weak annual aquatic herb 20–25 cm tall. Stems and leaves dimorphic. Primary stems robust, 2–7 cm tall, sparsely branched; leaves alternate, succulent, obovoid, entire, 6–8 mm long; secondary stems filiform, 15–20 cm long, freely branched; leaves floating, alternate, clustered at stem tip, petiolate, ovate; lamina 1.8–4.5 mm long. Bracteoles filiform, 1 mm long. Flowers 4-merous, sessile, solitary, adnate to petiole of floating leaves. Sepals narrowly deltoid, 0.2 mm long. Petals 0.8–1.2 mm long, persistent. Stamens 4 or 8. Ovary 4-locular; styles filiform; stigmas non-fimbriate. Fruit cruciform, black; mericarps divergent, fused only at apex, obovoid to cylindrical, 1.1–1.2 mm long, verrucose or striate.