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water-hyssop

disc waterhyssop, disk water-hyssop, round-leaf water-hyssop, wet waterhyssop

Habit Herbs, annual or perennial, emergent or submerged, sometimes rooting from proximal nodes. Annuals [perennials].
Stems

prostrate or erect, glabrous or slightly hairy.

prostrate, 15–60 cm, hairy, sometimes sparsely so, glabrescent.

Leaves

cauline, opposite [whorled];

petiole obscure or absent;

blade fleshy (B. monnieri) or not, not leathery, margins entire, crenate, or serrate.

hairy;

blade base broadly cuneate, margins entire, apex ± rounded.

Inflorescences

axillary, flowers solitary or in pairs;

bracts absent.

Pedicels

present or absent;

bracteoles present [absent].

9–15 mm.

Flowers

bisexual;

sepals 4 or 5, distinct, outer wider than inner, ovate, lanceolate, or oblong, calyx radially or bilaterally symmetric, campanulate;

corolla white (sometimes with yellow throat), pink, or violet-blue, radially or bilaterally (B. repens) symmetric, regular or weakly bilabiate, rotate or campanulate, rarely tubular, tube base not spurred or gibbous, throat not densely pilose internally, lobes 4 or 5, abaxial 2 or 3, adaxial 2;

stamens 2–4, adnate to corolla, didynamous or equal, filaments glabrous;

staminode 0;

ovary 2-locular, placentation axile;

stigmas peltately flattened and semicapitate.

sepals 5, ovate to oblong, calyx bilaterally symmetric;

corolla white with yellow throat, 5–10 mm;

stamens 2–4, equal.

Fruits

capsules, dehiscence septicidal-loculicidal or loculicidal.

Seeds

80–120, brownish black, ellipsoid to cylindric, reticulate, wings absent.

× = 14.

2n

= 56.

Bacopa

Bacopa rotundifolia

Phenology Flowering May–Nov.
Habitat In water or on mud in lakes, ponds, pools, in and around marshes and ditches, ephemeral pools on rock outcrops.
Elevation 0–2300 m. (0–7500 ft.)
Distribution
from USDA
North America; Mexico; Central America; South America; West Indies; s Europe; Asia; Africa; Indian Ocean Islands (Madagascar); Australia
[BONAP county map]
from FNA
AL; AR; AZ; CA; CO; IA; ID; IL; IN; KS; KY; LA; MD; MN; MO; MS; MT; NC; ND; NE; NM; OK; SD; TN; TX; VA; WI; WY; AB; SK [Introduced in Europe (Greece, Spain)]
[WildflowerSearch map]
[BONAP county map]
Discussion

Species ca. 70 (7 in the flora).

Bacopa laxiflora (Bentham) Wettstein ex Edwall, native to Central America and South America, has been introduced to Mexico and may be expected in the flora area. Plants of B. laxiflora resemble B. monnieri; they differ by erect stems and acute leaf blade apices.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Bacopa rotundifolia is the most widespread member of the genus in the United States; it is invasive in rice fields.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Leaf blades 1-nerved.
B. monnieri
1. Leaf blades (3–)5–9+-nerved.
→ 2
2. Plants aromatic; bracteoles present; corollas violet-blue with violet-blue throats.
B. caroliniana
2. Plants not aromatic; bracteoles absent; corollas white with yellow or white throats or pink with pink throats.
→ 3
3. Leaf blade bases narrowly cuneate.
→ 4
4. Leaf blade margins crenate.
B. egensis
4. Leaf blade margins entire.
B. repens
3. Leaf blade bases broadly cuneate to truncate.
→ 5
5. Pedicels 6–10 mm; corollas 2–5 mm, white with white throats.
B. innominata
5. Pedicels 9–51 mm; corollas 5–14 mm, white with yellow throats.
→ 6
6. Pedicels 9–15 mm; corollas 5–10 mm.
B. rotundifolia
6. Pedicels 17–51 mm; corollas 10–14 mm.
B. eisenii
Source FNA vol. 17, p. 260. Author: Adjoa Richardson Ahedor. FNA vol. 17, p. 261.
Parent taxa Plantaginaceae Plantaginaceae > Bacopa
Sibling taxa
B. caroliniana, B. egensis, B. eisenii, B. innominata, B. monnieri, B. repens
Subordinate taxa
B. caroliniana, B. egensis, B. eisenii, B. innominata, B. monnieri, B. repens, B. rotundifolia
Synonyms Monniera rotundifolia, B. nobsiana, B. simulans, Bramia rotundifolia, Macuillamia rotundifolia
Name authority Aublet: Hist. Pl. Guiane 1: 128, plate 49. (1775) — name conserved (Michaux) Wettstein: in H. G. A. Engler and K. Prantl, Nat. Pflanzenfam. 67[IV,3b]: 76. (1891)
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