Above a small naked stalk, the spadix bears a whorl of 4 to 9 male flowers. The mature seeds still possess both integuments. The inner one collapses while the outer swells to several cell layers. The embryo sac is replaced by abundant starch that fills most of the seed content. The globular embryo is located under the micropyle with its shoot apex towards the seed base.
Pollen is shed as yellow, dry, coherent thread or mass, finally falling down to the spathe.
The tissue of both organs consists of densely packed, isodiametric cells and contains no intercellular spaces. The inception of the collar is earlier than that of the scale, and they differ in their position. Such sterile flowers are found in Aroideae as well. Reproduction Ecology Dispersal of Pistia generally takes place by vegetative transport of young rosettes, either by water currents or by animals. Different from all member of Araceae, this plant forms no vegetative persisting organs, but dies down completely in dry or cold seasons.