Plant: annual aquatic or terrestrial herb; in water, mostly submerged but usually with a floating rosette of leaves Leaves: polymorphic; submerged leaves linear, 1-15 mm long, 0.3-1.0 mm wide, the margins entire, the apices bifid or emarginate with the single nerve often extending to a callous point, the bases clasping the stem, the leaf base pairs usually adjoining or less often separated by a ridge or wing at the node; floating or terrestrial leaves petioled, 3-nerved, obovate to oblanceolate to spatulate, 1-15 mm long, 1-5 mm wide, the marginsentire, the apices rounded to slightly retuse, the bases as above, the surface covered with minute scales and appearing punctate INFLORESCENCE: with usually 1 staminate and 1 pistillate flower in each axil Flowers: subtended by a pair of whitish inflated bracteoles, 0.5-1.5 mm long, usually deciduous in fruit; styles 1-6 mm long, erect or spreading, often persistent Fruit: nutlets, brown at maturity, sessile, 0.5-1.4 mm long, 0.6-1.2 mm wide, usually 0.2 mm longer than wide, obovate, the margins flattened, winged (conspicuous on mature material), widest at the apex, often inconspicuous on the sides and bases, the groove between carpels evident between the wings, the surface pits appearing more or less aligned in vertical rows Misc: Lakes, ponds and slow-moving streams; 2050-2850 m (6700-9400 ft); May-Aug (fr. Aug-Oct) REFERENCES: Ricketson, Jon. 1995. Callitrichaceae. J. Ariz. - Nev. Acad. Sci. 29(l): 15.

Annual submersed aquatic herb 10 - 20 cm tall Stem: slender, loosely clustered, with roots forming on lower nodes and shoot tips often floating. Leaves: of two types, submersed and floating. Submersed leaves are opposite, 0.5 - 1.5 cm long, linear, and non-toothed. Floating leaves (if present) opposite or form a terminal rosette, 3 - 10 mm long, 1.5 - 5 mm wide, spoon-shaped with a rounded tip, non-toothed. Flowers: either male or female, found on the same plant (monoecious), often with one male and one female per axil, green, tiny, bracts (two) whitish, lacking sepals and petals, with stigmas as long as the fruit. Fruit: separating into four dry nutlets at maturity, stalkless, 1 - 1.4 mm long, about 0.2 mm longer than wide, inversely egg-shaped and narrowing near the base, dotted with tiny pits in distinct vertical rows, winged, with distinct groove between the wings.

Similar species: Callitriche heterophylla and Callitriche verna are very similar species that are most easily distinguished by their fruit. The fruit of C. heterophylla is less than 1 mm long and equally wide, rounded at the base, lacks wings, and is dotted with tiny pits that do not form distinct rows.

Flowering: late May to September

Habitat and ecology: Rare in the Chicago Region, Callitriche verna is considered a circumboreal species, meaning it is a northern species occuring in both Eurasia and America. In this region, it usually grows in calm, calcareous waters.

Occurence in the Chicago region: native

Notes: This species provides food and shelter for aquatic insects and fish. The seeds and leaves are eaten by ducks.

Etymology: Callitriche comes from the Greek words, kalli, meaning beautiful, and thrix, meaning hair, referring to the slender stems. Verna comes from the Latin word meaning spring.

Author: The Morton Arboretum

Slender annuals, rooting at the lower nodes, with loosely clustered stems 1-2 dm, typically growing mainly submerged with only the shoot-tips floating, but sometimes stranded in mud and wholly emersed, rarely wholly submersed; submersed lvs linear, 0.5-1.5 cm; floating or emersed lvs spatulate to obovate, to 5 mm wide, triplinerved, appearing finely and sparsely lepidote at 10נor 20׻ bracteoles whitish, 0.5-1.5 mm, deciduous; usually one male and one female fl per axil; frs mostly 1-1.4 mm long and ca 0.2 mm longer than wide, widest above the middle, compressed and with a broad, shallow groove down the middle of each side, and also with an evident commissural groove on each edge, narrowly winged (or at least sharp-edged) on each side of the commissural groove toward the summit, less (or scarcely) so below; pit-like markings on the fr tending to be aligned in vertical rows; 2n=20. In quiet water; circumboreal, in Amer. s. to W.Va., Nebr., Tex., and Calif.; also in S. Amer. (C. verna)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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