1. Brasenia schreberi J.F. Gmel. (water shield, snot plant)

Pl. 329 a, b; Map 1398

Plants apparently glabrous (although the mucilage is secreted by minute glandular hairs, these are not apparent on mature herbage), the submerged portion, including the undersurface of the leaf blades, covered with a thick layer of a jellylike mucilaginous substance. Leaves monomorphic, sometimes submerged in young plants, but mostly with floating blades, long-petiolate (to 30 cm or more). Leaf blades 3.5–13.5 cm long, 2–8 cm wide, peltate, broadly elliptic, the margins entire, the undersurface dark reddish purple. Flowers mostly long-stalked, held just above the water at flowering, the stalk bending to become submerged as the fruits develop. Perianth curled outward and downward at flowering, later becoming erect and more or less enfolding the developing fruits. Sepals 3 or less commonly 4, 13–15 mm long, strap-shaped, green on the outer surface, reddish purple to maroon on the inner surface. Petals 3 or less commonly 4, slightly longer and narrower than the sepals, strap-shaped, reddish purple to maroon. Stamens 18–36 (rarely more). Pistils 4–18, the style with a linear stigmatic region along a side toward the tip. Fruits 6–10 mm long, club-shaped to peanut-shaped, tapered to the persistent style. Seeds 2.5–4.0 mm long, oblong to oblong-ovate in outline, the surface finely pebbled, grayish brown to yellowish brown. 2n=80. May–September.

Scattered, mostly in southern and eastern Missouri (nearly throughout the U.S., except for some western states; Canada, Mexico, Central America, Caribbean Islands, Asia, Africa, Australia). Floating-leaved aquatics in ponds, lakes, and sloughs.

Water shield is of food value to waterfowl, and the tuberous roots reportedly were eaten by Native Americans in California. The thick, jellylike coating of the submerged parts presumably retards drying out of the plants when water levels drop during droughts and may also help to deter mammals from eating the herbage. The young leaves and petioles, before the gelatinous covering becomes prominent, also have served as salad greens in parts of Japan. The floating leaves afford shade and shelter for fish and other aquatic organisms. However, the species can become a nuisance, especially in shallow ponds and lakes, where it can cover the water surface so thickly as to preclude light and gas exchange. It undoubtedly is more widespread in Missouri than the specimen data suggest.