Variation in Leaf Form in Callitriche intermedia

Abstract

Callitriche intermedia shows a well-marked variation in its leaf form, dependent on whether the crown of the plant is submerged or floating at the surface of the water. When the crown is submerged, linear leaves are produced, up to 3 cm. in length and 1 mm. broad. When the crown reaches the surface, ovate leaves are produced, about 1.5 cm. long and 4 mm. broad at the widest point. A reversion to the linear type of leaf is produced if the crown is afterwards submerged.