1. Marsilea quadrifolia L. (European
water-clover) Pl. 8a,b; Map 42
Roots at nodes of the rhizome and sparsely between the nodes. Leaves
cloverlike, with 4 leaflets. Petioles 5–16 cm long. Leaflets 7–20 mm long,
glabrous or pubescent. Sporocarps 4.0–5.5 mm long, oval to elliptic, flattened,
hairy or becoming nearly glabrous, lacking a well-defined tooth at the
attachment point, arising 1–3 per node from near the base of the petiole on an
unbranched or branched peduncle 3–16 mm long, when branched the branches 2–12
mm long, erect to spreading. 2n=40. August–October.
Introduced, uncommon in Barton and Platte
Counties (Europe, Asia; widely
introduced in the eastern U.S.).
Floating-leaved aquatic in ponds and lakes, sometimes stranded on mud.
Previous reports of M. vestita Hook. & Grev. (M. mucronata A.
Braun) from Missouri
were based upon misdetermined specimens of M. quadrifolia (Johnson,
1985a).