Callitriche L.
Submerged lvs usually linear; floating lvs and those of terrestrial plants narrow-spathulate to ovate, often forming a terminal rosette.
Key
Lower, earlier and usually submerged lvs 3-7-nerved, linear-elliptic, linear-spathulate to spathulate or obovate
4
Submerged lvs similar to floating lvs; fr. > 1 mm diam., conspicuously and evenly winged all round
Submerged lvs markedly narrower than floating lvs; fr. < 1 mm diam., winged at top only
Lvs spathulate or obovoid, sometimes suborbicular, usually entire; wing < ⅓ width of mericarp or 0
A
Dioecious; lvs 1-1.5 mm long; fr. 0.6-0.7 × 0.7-0.9 mm
subsp petriei
Monoecious; lvs 2.5-8 mm long; fr. 0.6-0.9 × 0.7-1.1 mm
subsp chathamensis
25 spp., cosmopolitan. Native spp. 4, naturalised 3.
There can be great variation within one sp. of Callitriche at a particular site; in particular the extent to which the amphibious habit is adopted varies according to water depth.
