CALLITRICHACEAE

WATER-STARWORT FAMILY

C. Thomas Philbrick

Annual, in water or on wet ground, monoecious
Stem slender, generally ascending under water, floating on surface, or prostrate on ground, generally much-branched
Leaves simple, generally opposite, 4-ranked, linear-lanceolate to spoon-shaped, entire; stipules 0
Inflorescence: flowers 1–3 per leaf axil, the group subtended by generally 2 whitish, inflated bracts
Flowers minute, unisexual; perianth 0
Staminate flower: stamen generally 1, filament elongate
Pistillate flower: ovary superior, ± obcordate, chambers 4, styles 2, thread-like
Fruit 0.6–1.6 mm (width generally ± = length), ± dry, ± grooved longitudinally, splitting into 4 achene-like units
Recent taxonomic note: Recently treated in expanded Plantaginaceae (= Veronicaceae sensu Olmstead et al.) that includes genera removed from Scrophulariaceae [Angiosperm Phylogeny Group 1998 Ann Missouri Bot Gard 85:531–553; Olmstead et al. 2001 Amer J Bot 88:348–361]
Horticultural information: DRN, DRY, SUN; DFCLT.

CALLITRICHE

WATER-STARWORT

The only genus,
Species in genus: ± 40 species: tropical, temp
Etymology: (Greek: beautiful hair, from slender stems)
Reference: [Fassett 1951 Rhodora 53:137–155,161–182, 185–194,209–222; Philbrick & Jansen 1991 Syst Bot 16:478–491]
Taxonomically difficult; mature fruit and 10X magnification needed for identification.

Native

C. trochlearis Fassett

Plant mat-forming at water edge or with floating rosettes
Leaves: submersed leaves linear-lanceolate; floating, emergent, or terrestrial leaves spoon-shaped
Inflorescence: bracts subtending flowers 2, whitish, inflated, persistent in young fruit
Fruit 1–1.5 mm long, wide, dark brown to black; groove shallow; wing uniformly wide from base to tip, transition to fruit wall abrupt; pedicel generally 0–0.5 mm
Ecology: Becoming stranded or submersed < ± 6 dm
Elevation: < ± 500 m.
Bioregional distribution: Northwestern California, Central Western California
Distribution outside California: w Oregon