Vaucheria macounii Vishnyakov & Moseev 2024, comb. et stat. nov.

Vaucheria macounii (Blum) Vishnyakov, comb. et stat. nov. (Figs 2–13) Basionym:— V. longicaulis var. macounii Blum 1971, Bull. Torrey Bot. Club, 98(4): 193. Type:— ʻJ. Blum #1977, from open ground in salt marsh, south end of Sequim Bay, Washington, September 25, 1966, in Herb. New York Botanical Garden’. Morphology:— Filaments dioecious, rarely monoecious, sympodially branched, 32.5–50.0 µm in diam. Gametangia terminal. Antheridia commonly in clusters, separated from filament by wall-bound cavity, fusiform (spindle-shaped), fusiform-cylindrical, sometimes furcate, conical, curved, spirally twisted, 140–265 µm in length, 30–70 µm in diam., opening a terminal pore and 1–7 pores on lateral papillae (Figs 2–7). Antheridial papillae conical, pointed upwards, 2.5–37.5 µm in length. Oogonia club-shaped (pyriform), commonly curved, 220–410 µm in length, 87.5–122.5 µm in diam., without a distinctive fertilization pore (Figs 8–13). Oospores globose or ellipsoid, 92.5–135 µm in length, 77.5–122.5 µm in diam.; smaller lower portion of cytoplasm remaining after fertilization usually degenerates without forming wall material (remaining an amorphous mass in proximal part of the oogonium), leaving thin annular deposit on the oogonial wall, or forming a transverse wall and ultimately an empty cell. Asexual reproduction by club-shaped aplanospores forming in terminal sporangia, 250 µm in length, 130 µm in diam. (rarely seen).