Arrowhead
Sagittaria sagittifolia (also called arrowhead due to the shape of its leaves) is a flowering plant in the family Alismataceae, native to wetlands throughout the temperate regions of Europe and Asia; in Britain it is the only native Sagittaria.
It is a herbaceous perennial plant, growing in water from 10-50 cm deep. The leaves above water are arrowhead-shaped, the leaf blade 15-25 cm long and 10-22 cm broad, on a long petiole holding the leaf up to 45 cm above water level. The plant also has narrow linear submerged leaves, up to 80 cm long and 2 cm broad. The flowers are 2-2.5 cm broad, with three small sepals and three white petals, and numerous purple stamens.
Remnants of Sagittaria sagittifolia have been found in the Paleolithic/Mesolithic site of Calowanie in Poland.
Source: en.wikipedia.org/wiki/Sagittaria_sagittifolia - 07.12.2011
Arrowhead
Here we only see the eponymous leaf shape, the air leaves. In contrast to this the leaves lying on the water surface and the leaves lying underwater are oval or linear.
