Stuckenia pectinata (sago pondweed) - Potamogetonaceae. This is a rooted submersed aquatic species that is native throughout North America. The spike is comprised of whorls of flowers and the resulting fruits are clusters of semifleshy achenes (shown in upper right corner of photo). Stems are terete and dichotomously branched. Open, extremely long modified stipules make this species easy to identify from other similar pondweeds (you'll want to call these stipules ligules at first glance). See explanation in 'Aquatic and Riparian Weeds of the West' by DiTomaso and Healy (lots of good information on natives in that book). This species is Potamogeton pectinatus in Hitchcock.Some terms:
Dichotomous = branched or forked into two more or less equal divisions. Terete = round in cross-section; cylindrical. Achene = a small, dry, indehiscent fruit with a single locule and a single seed (ovule), and with the seed attached to the ovary wall at a single point. Locule = the chamber or cavity of an organ, as in the cell of an ovary containing the seed or the pollen bearing compartment of an anther.
