1. Ammannia L. (toothcup)(Graham, 1985)

Plants terrestrial or strongly emergent aquatics, annual, fibrous-rooted, sometimes rooting at the lower nodes, not producing offsets at the base, glabrous. Stems erect or strongly ascending, not wandlike, strongly 4-angled (square in cross-section), usually branched from near the base, the branches spreading to arched upward, not rooting at the tip. Leaves opposite, sessile. Leaf blades linear to narrowly lanceolate, narrowly oblong-triangular, or narrowly oblanceolate (in some lower leaves of A. robusta), those of the largest leaves always 3 mm or wider), narrowed or tapered to a usually sharply pointed tip, all truncate to more commonly auriculate-cordate at the base. Inflorescences of small axillary clusters of (1–)3–5(–14) flowers, sessile or more commonly the cluster on a stalk to 4(–9) mm long. Flowers actinomorphic, the hypanthium about as long as wide, cup-shaped to urn-shaped (sometimes becoming nearly globose at fruiting), symmetric at the base (not pouched or spurred), not oblique at the tip, with 4 or 8 longitudinal ridges (these best developed at fruiting). Sepals 4, triangular, the appendages shorter than to about as long as the sepals, thickened, more or less linear. Petals 4, 1.5–3.0 mm long, pink to purple or pale lavender, not persistent at fruiting. Stamens 4(–8), those of different flowers with filaments the same length, the anthers exserted, yellow. Pistils lacking a nectary disc, the ovary incompletely 3- or 4-locular, the style relatively long and exserted (very short elsewhere). Fruits globose to oblong-globose (excluding the often persistent style) capsules, dehiscing irregularly with age, the outer wall smooth. Seeds numerous, 0.7–1.0 mm long, asymmetrically ovoid (1 side concave, the other convex), the surface with a network of fine, sometimes faint ridges, brown. About 25 species, nearly worldwide, most diverse in Africa.