Morphology of flower, fruit and seed in Polypleurum stylosum

Abstract

Polypleurum stylosum (Wight) Hall, a member of the family Podostemaceae, lacks the conventional differentiation into root and shoot. The profusely branched thallus inhabits the gushing waters of rivers and streams, and is attached to rocks and stones by means of rhizoids and haptera. Flower buds present along the margins of the thallus are enclosed in a spathe sustained by two or three pairs of bracts. The laterally placed ovary has a very short style and two stigmas, of which the upper one is bifid. There are two stamens with their filaments fused at the based and two staminodes. Each flower produces about 3100±400 pairs of echinate pollen grains. The total number of ovules per ovary is 400±20. Fruits are stalked, isolobous and eight-ribbed, opening by means of two or three septicidal slits, and contain about 245±25 seeds. The seeds are non-endospermous and minute; 1 g weight contains about 700 000 seeds.