Azolla-Click for more info

An Azolla plant consists of a short, branched, floating stem, bearing roots which hang down in the water. Each leaf is bi-lobed, the upper lobe containing green chlorophyll while the lower lobe is colourless. Under certain conditions, an anthocyanin pigment, also occurs giving the fern a reddish-brown colour. This is particularly associated with over-fertilization of ponds, pollution and excess sunlight. Shaded conditions are preferred to full exposure to tropical sunlight.
The plant is highly productive with the ability to double its weight in 7 days.  Because the fern can form dense mats on water surfaces, it is classified as a water weed in many areas.  AFRIS