 Azolla cristata

Azolla cristata , the Carolina mosquitofern, Carolina azolla, or water velvet, is a species of "Azolla" native to the Americas, in eastern North America from southern Ontario southward, and from the east coast west to Wisconsin and Texas, and in the Caribbean, and in Central and South America from southeastern Mexico (Chiapas) south to northern Argentina and Uruguay.It is a freshwater aquatic fern, with scale-like fronds 5–10 mm long, green to reddish, most often reddish in strong light and in winter.