Myriophyllum muelleri

Slender perennial aquatic herb; stems to 60 cm long, c. 1 mm diam., rooting mainly at the base, emergent parts branched. Leaves mostly decussate, lowermost rarely in whorls of 3, uppermost sometimes alternate, orbicular, mostly 5–11 mm long, pectinate, with 12–16 pinnae. Bracteoles of male flowers ovate to orbicular, c. 1.3 mm long, apiculate, white; bracteoles of female flowers similar, c. 0.4 mm long; flowers solitary. Male flowers terminal, usually single, on a slender peduncle to 20 mm long and on a receptacle 0.4–1 mm long, enclosed in a hooded bract; sepals 4, vestigial; petals 4, 2.1–2.2 mm long, red, deciduous; stamens 8. Female flowers sessile, naked, 2–4 per branch of inflorescence, situated below male flower; sepals and petals absent; ovary 4-celled, styles teardrop-shaped, creamy-yellow, stigmas smooth. Fruit cylindric, silvery-grey to reddish; mericarps cylindric, 1.7–1.8 mm long, truncate, smooth. Flowers Sep.–Feb.