Water stars

--- CONTENT ---
Water stars (Callitriche) form a plant genus within the plantain family (Plantaginaceae).

Description

Vegetative characteristics
The water stars are creeping herbaceous plants living on the ground or partially or completely below the surface of the water, from one to more years old. The shoot axis grows in thread form and is set with opposing, side-leafless foliage leaves. The shape and arrangement of the leaves varies greatly depending on the location. Submerged plants often have lancet or ruler leaves and long internodes. Plants whose shoot axis grows above the water have shorter internodes, so that the then elliptical or spatula-shaped leaves stand in rosettes. Terrestrial growing plants usually have egg-shaped or almost circular leaves. In the armpits of the shoot axis stand gland scales, both shoot axis and foliage leaves are set with scale-shaped trichomes.

Generative characteristics
The water star species are monoecious (monecious) or biecious (diocese) separated sex. The one-sex flowers are in the armpits and occur either individually or in pairs with a male and a female flower. There is no flower cover, two supporting leaves are pronounced in the shape of a crescent or are also missing. The male flowers usually consist of only a single, rarely up to three stamens / dust leaves with a slender dust thread and a kidney-shaped dust bag. In the female flowers, two fruit leaves have grown into an upper fruit knot divided into four chambers by a false vaginal wall. Each fruit knot chamber contains a single anatropic seed plant. The two free pens are thread-shaped.

The fruit is a decay fruit that breaks down into four lonely, more or less winged partial fruits. The seeds have a fleshy endosperm.

Nomenclature and distribution
Callitriche was created by Carl von Linné. The generic name Callitriche is derived from Greek words kallos for physical beauty and thrix and trichos for hair (because of the growth form).

The position of the genus Callitriche within the covered seeds was long unclear due to a lack of characteristics, especially due to the greatly reduced flowers. In part, they were led in a monogeneric family Callitrichaceae. According to knowledge of molecular biology, they are classified in the family of plantain plants (Plantaginaceae).

The genus of water stars (Callitriche), occurs with 25 to 30 species worldwide (with the exception of South Africa).

The following water star species were detected in Germany:

Sticked water star (Callitriche brutia, Syn.: Callitriche pedunculata): It occurs in southern and western Europe, east to Italy, north to southern Sweden.
dull-edged water star (Callitriche cophocarpa),