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Published In: Die Natürlichen Pflanzenfamilien 67[IV,3b]: 76. 1891. (Nat. Pflanzenfam.) Name publication detail

Project Name Data (Last Modified On 9/1/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native


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1. Bacopa rotundifolia (Michx.) Wettst. (water hyssop)

Pl. 480 e, f; Map 2193

Plants annual or perennial herbs, with fibrous roots, aquatic or sometimes terrestrial when stranded on mud. Stems (5–)10–60 cm long, at least the lower portion usually submerged, the apical portion weak and floating on water (occasionally entire plant floating), when terrestrial then prostrate to loosely ascending, rooting at the lower nodes, not angled, moderately to densely and finely short- hairy, at least on newer growth. Leaves opposite, sessile. Leaf blades 1.0–3.5 cm long, (8–)10–28 mm wide, relatively thick (but drying very thin and fragile), broadly spatulate to more commonly broadly oval or circular, unlobed, rounded at the tip, shallowly cordate to rounded or broadly angled at the base, mostly at least slightly clasping the stem, the margins entire, but sometimes finely short-hairy, the venation palmate with 5–9 main veins, the surfaces glabrous or nearly so at maturity, the upper surface somewhat shiny. Inflorescences axillary, the flowers 1 or 2(–4) per leaf axil, the flower stalks 6–23 mm long; bractlets absent. Flowers perfect. Calyces 3.0–4.5 mm long at flowering, becoming enlarged to 4–6 mm at fruiting, deeply 5-lobed nearly to the base, glabrous, the outer 3 lobes leaflike, ovate to broadly ovate, the inner 2 inconspicuous, lanceolate. Corollas 4.5–9.0 mm long, not bilabiate, weakly zygomorphic, 5-lobed, glabrous, the tube slightly shorter than to about as long as the lobes, white or less commonly very pale pinkish-tinged with a yellow throat, spurless, the throat open, the lobes collectively bell-shaped above the slender tube, individually oblong-obovate with more or less truncate but shallowly notched tips. Fertile stamens 4, the filaments of 2 lengths, not exserted, the anthers attached near their midpoints, the anther sacs parallel; staminodes absent. Style 1, not exserted, forked near the tip, each branch with an expanded, irregularly oval, cushionlike stigma at the tip. Fruits capsules, 3.5–5.5 mm long, globose to broadly ellipsoid, glabrous, the 2 locules equal in size, dehiscent longitudinally by 4 valves. Seeds numerous, 0.4–0.6 mm long, ellipsoid to cylindric with a minute tail-like appendage at each end, not flattened, the surface yellowish brown, with a network of fine ridges. 2n=36. May–September.

Scattered south of the Missouri River, uncommon farther north (eastern U.S. [except some northeastern states] west to Idaho and Arizona; Canada; introduced in California and Asia). Floating or mostly submerged aquatics in shallow water of ponds, lakes, sinkhole ponds, swamps, and sloughs, less commonly in backwater areas of streams; also ditches and rice fields; sometimes stranded on wet mud.



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