[*][*] Flowers irregular and unsymmetrical, with 6 petals and 11 stamens.
6. Cuphea. Calyx spurred or enlarged on one side at base. Petals unequal.
1. DIDÍPLIS, Raf. Water Purslane.
Calyx short-campanulate or semiglobose, with no appendages at the sinuses (or a mere callous point). Petals none. Stamens 4, short. Capsule globular, indehiscent, 2-celled.—Submersed aquatic (sometimes terrestrial), rooting in the mud, with opposite linear leaves, and very small greenish flowers solitary in their axils. ("Didiplis means two doubling;" from δíς, twice, and διπλóος, double.)
1. D. lineàris, Raf. Leaves when submersed elongated, thin, closely sessile by a broad base, when emersed shorter and contracted at base; calyx with broad triangular lobes; style very short; capsules very small. (Ammannia Nuttallii, Gray.)—From Minn. and Wisc. to Tex., east to N. C. and Fla.
2. ROTÀLA, L.
Calyx short-campanulate or semiglobose, with tooth-like appendages at the sinuses (abnormally, in our species). Petals 4 (in ours). Stamens 4, short. Capsule globular, 4-celled, septicidal, the valves (under a strong lens) transversely and densely striate. (Name a diminutive of rota, a wheel, from the whorled leaves of the original species.)
1. R. ramòsior, Koehne. Leaves tapering at base or into a short petiole, linear-oblanceolate or somewhat spatulate; flowers solitary (rarely 3) in the axils and sessile; accessory teeth of calyx as long as the lobes or shorter. (Ammannia humilis, Michx.)—Low or wet ground, Mass. to Fla., west to Ind., Kan., and Tex.—With Ammannia-like habit, an exception in the genus.
3. AMMÁNNIA, Houston.
Flowers in 3–many-flowered axillary cymes. Calyx globular or bell-shaped, 4-angled, 4-toothed, usually with a little horn-shaped appendage at each sinus. Petals 4 (purplish), small and deciduous, sometimes wanting. Stamens 4–8. Capsule globular, 2–4-celled, bursting irregularly.—Low and inconspicuous smooth herbs, with opposite narrow leaves, and small flowers in their axils, produced all summer. (Named after Paul Ammann, a German botanist anterior to Linnæus.)