Callitriche L.

Scientific Description

Family Callitrichaceae.

Habit and leaf form. Aquatic, amphibious or terrestrial herbs. Annual, or perennial; plants with neither basal nor terminal concentrations of leaves, or with terminal rosettes of leaves. Hydrophytic, or helophytic; rooted. Leaves of aquatics submerged, or emergent, or submerged and emergent. Heterophyllous (usually), or not heterophyllous. Leaves opposite (decussate, to rosetted towards branch tips), or whorled (rarely); not gland-dotted; simple, or simple and compound (linear and bifid when submerged); epulvinate. Leaf blades dissected, or entire; when dissected, dichotomously dissected. Leaves without stipules. Leaf anatomy. Hairs absent. Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers functionally male and functionally female, or functionally male, or functionally female. Unisexual flowers present. Plants monoecious, or dioecious. Sometimes pollinated by water.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’ (then 1 male and 1 female flower together); when solitary axillary. Inflorescences axillary. Flowers commonly bracteolate (the bracteoles hornlike); minute. Perianth absent. Fertile stamens present (male flowers), or absent (female flowers). Androecium 1(–3). Androecium exclusively of fertile stamens. Stamens 1(–3). Anthers reniform to circular in outline; dehiscing via longitudinal slits (that are apically confluent). Fertile gynoecium present (female flowers), or absent (male flowers). Gynoecium 2 carpelled. The pistil 4 celled. Gynoecium syncarpous; synovarious; superior. Ovary plurilocular; 2 locular (morphologically), or 4 locular (ostensibly, via a ‘false septum’). Locules secondarily divided by ‘false septa’. Ovary sessile. Styles 2; free; from a depression at the top of the ovary; apical. Stigmas 2; papillate. Placentation apical. Ovules 2 per locule (i.e. 2 per ‘carpel’), or 1 per locule (per locellus); pendulous; anatropous.

Fruit and seed features. Fruit non-fleshy; a schizocarp. Mericarps 4; comprising nutlets (the mericarps winged or keeled). Seeds 1 per mericarp. Seeds endospermic (the endosperm fleshy). Cotyledons 2. Embryo straight. Seedling. Germination phanerocotylar.

Geography, cytology, number of species. Adventive. Australian states and territories: Western Australia. South-West Botanical Province.