4. Najas minor All. (brittle naiad)

Pl. 110 e, f; Map 453

Stems 10–30 cm long. Leaves 0.5–3.5 cm long, 0.1–0.6 mm wide, ascending to spreading and becoming recurved late in the growing season, serrulate with multicellular teeth usually visible without magnification, the tip acute. Leaf bases abruptly broadened into stipular sheaths, the sheaths auriculate. Seeds 1.5–3.0 mm long, narrowly fusiform to cylindrical, curved to 1 side at the tip, the surface purplish brown, dull, finely pitted with 12–18 rows of dense, ladderlike pits that are short, broad, and rectangular. 2n=12. July–September.

Introduced in southern and eastern Missouri (native of Europe, widely naturalized in the eastern U.S., west to Arkansas). Submerged aquatic in ponds and lakes.

This species was first discovered in North America in the Hudson River in 1934 (Meriläinen, 1968). It has since spread rapidly, apparently by migrating waterfowl. It was first noted in Missouri by Whitley et al. (1990) and will surely become more widespread in the future.