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. hermaphroditica L.

Leaves submersed, linear-lanceolate
Inflorescence: bracts subtending flowers 0
Fruit 1.1–1.6 mm, 1.2–1.8 mm wide; wing variable, transition to fruit wall abrupt; pedicel 1–3 mm
Ecology: Submersed in quiet streams, ponds
Elevation: < ± 2000 m.
Bioregional distribution: Sierra Nevada, Great Central Valley, Central Western California, Modoc Plateau
Distribution outside California: to Canada, e US