Species: Howellia aquatilis

Water Howellia is a glabrous, much-branched, annual, aquatic herb with fragile, submerged and floating stems that are up to 100 cm tall. The simple, alternate or occasionally opposite or whorled stem leaves are narrowly linear, 1-5 cm long, and entire-margined. Beneath the surface of the water, small flowers that produce seeds without opening are solitary in the leaf axils. Once the stems reach the surface, small, white flowers are borne in a narrow, terminal, leafy-bracted inflorescence. The white corolla is 2-3 mm long. Flowering occurs on the surface of the water. The fruit, which forms below the attachment of the petals, is a capsule that is 1-2 cm long containing elongate seeds that are up to 2-4 mm long.