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.