Bacopa rotundifolia (Michaux) Wettstein. Section: Herpestis. Midwestern Water-hyssop. Phen: May-Sep (-Nov). Hab: Tidal muds, shallow water of large natural lake, river sandbars, other shallow water and shore situations. Dist: IN and IA west to ND and MT, south to AL and AZ; disjunct in e. MD, e. VA, ne. NC, and e. SC (Bradley et al. [in prep.]), where apparently native, though Cronquist (1991) considered introduced. Known in NC only from Lake Mattamuskeet, Hyde County, and "north of Wilmingon); not recently seen.

Origin/Endemic status: Native

Taxonomy Comments: B. simulans Fernald has been considered a rare endemic of tidal areas in VA and MD. It is alleged to differ from B. rotundifolia in its glabrous to glabrescent stems (vs. pubescent), more succulent condition, smaller leaves (the larger 1-2 cm long and 0.6-1.5 cm wide vs. 2-3.5 cm long and 1.5-2.7 cm wide), smaller flowers (corolla 3-4 mm long vs. 6-10 mm long). Schuyler (1989) concluded that B. simulans is an intertidal form of B. rotundifolia, the morphologic differences the result of differences in inundation. Additional work, perhaps involving growth under experimental conditions or chemical or molecular studies, is needed to corroborate Schuyler's conclusion. See Schuyler (1989), F, and Fernald (1942) for further discussion.

Synonymy: = Ar, C, FNA17, GrPl, GW2, Il, K1, K3, K4, NcTx, Tn, Tx, Schuyler (1989); = Macuillamia rotundifolia (Michx.) Raf. – S, Pennell (1935); = n/a – RAB, Tat; > Bacopa rotundifolia (Michx.) Wettst. – F, G; > Bacopa simulans Fernald – F, G

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: OBL
• Eastern Mountains and Piedmont: OBL
• Great Plains: OBL
• Midwest: OBL
• Northcentral & Northeast: OBL

Heliophily: 8