Salviniaceae

Common water fern ( Salvinia natans ), illustration

The Schwimmfarngewächse family is among the ferns.

Features

Roots are present ( Azolla ) or absent ( Salvinia ). The shoot axis is a protostele which is branched dichotomously. The leaves are sessile, alternate, and small ( 1-25 mm). The leaf shape is elongated with whole leaf edge. The Blattnervatur is free ( Azolla ) or anastomosing ( Salvinia ).

The plants are heterosporous: large megaspores and small microspores. Germination occurs in the spores.

The basic chromosome number is x = 9 at Salvinia ( the smallest known in ferns ) in Azolla x = 22

Occurrence

The family is subkosmopolitisch common. There are free-swimming species.

System

Today, in this family the two genera Salvinia and Azolla are summarized, which were long managed as separate families:

• Floating ferns ( Salvinia seg. ), With about 8-12 species
• Algae ferns ( Azolla Lam. ), With about 3 to 6 species

The family is known fossil since the Cretaceous.