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. marginata Torr.

Plant mat-forming at water edge or with floating rosettes
Leaf narrowly to widely spoon-shaped
Inflorescence: bracts subtending flowers 2, whitish, inflated, persistent in fruit or not, 0 on terrestrial plants
Fruit 0.7–1.4 mm, 0.9–1.4 mm wide, maturing underground on terrestrial plants; wing 0 to wide; pedicel 1–25 mm
Ecology: Becoming stranded (often in vernal pools) or submersed < ± 6 dm
Elevation: < ± 1500 m.
Bioregional distribution: California Floristic Province
Distribution outside California: to British Columbia, Baja California
Synonyms: C. longipedunculata Morong