Suckenia filiformis (Pers.) Boerner (formerly Potamogeton filiformis): Threadleaf pondweed, fineleaf pondweed, slender-leaved pondweed. Potamogetonaceae (pondweed family). Native perennial. Whole plant is very slender and thread-like, to 20 in (50 cm) tall, growing submersed and with only one type of leaf. Stems emerge from a network of rhizomes that can form tubers at their tips. Stems to 0.04 in (1 mm) wide, and slightly flattened, branching into two near the base of the plant. Leaves are very thin, 2 - 4.75 in (5 - 12 cm) long; they have one main vein. The lower part of the stipule sheathes the stem and the base of the leaf blade; the upper part is free of the stem and up to 0.2 in (0.5 cm) long. The stipule can be pulled away from the stem to reveal the lower part of the leaf blade. Flower spike stalks are slender to thread-like; the flowers and later nut-like fruits are spaced rather than crowded along the stalk.