Order 41. LYTHRÀCEÆ. (Loosestrife Family.)
Herbs, with mostly opposite entire leaves, no stipules, the calyx enclosing but free from the 1–4-celled many-seeded ovary and membranous capsule, and bearing the 4–7 deciduous petals and 4–14 stamens on its throat; the latter lower down. Style 1; stigma capitate, or rarely 2-lobed.—Flowers axillary or whorled, rarely irregular, perfect, sometimes dimorphous or even trimorphous, those on different plants with filaments and style reciprocally longer and shorter. Petals sometimes wanting. Capsule often 1-celled by the early breaking away of the thin partitions; placentæ in the axis. Seeds anatropous, without albumen.—Branches usually 4-sided.
[*] Flowers regular or nearly so.
[+] Flowers mostly solitary in the axils of the leaves, sessile or nearly so.
1. Didiplis. Calyx short, without appendages. Petals none. Stamens 4. Capsule indehiscent. Small aquatic.
2. Rotala. Calyx short, the sinuses appendaged. Petals and stamens 4. Capsule septicidal, with 3–4 valves.
3. Ammannia. Flowers not trimorphous. Petals generally 4 or none. Stamens 4. Capsule bursting irregularly.
[+][+] Flowers in 3–many-flowered axillary cymes (rarely solitary).
4. Lythrum. Calyx tubular. Petals usually 6. Stamens mostly 6 or 12. Flowers cymose-spicate in one species.
5. Decodon. Flowers trimorphous. Petals 5 (rarely 4). Stamens 8–10. Capsule 3–4-valved, loculicidal.