1. Ceratophyllum demersum L.

Pl. 351 e–g; Map 1509

Leaf blades 1.5–2.5 cm long, divided 1 or 2(3) times dichotomously into 3 or 4(–6) segments, rarely undivided, the marginal teeth relatively prominent, with the spinelike or bristlelike point ascending or somewhat spreading on the broadly triangular base of tissue, giving the leaves a minutely spiny appearance, even to the naked eye. Fruits with the surfaces smooth or slightly warty, the rim 3-spined (1 terminal stylar spine and 2 basal spines). 2n=24. June–September.

Common nearly throughout the state (worldwide). Submerged aquatic in slow-moving waters of streams, rivers, and spring branches, and still waters of ponds, lakes, and sloughs.