About Azolla filiculoides Lam.
Identification: The only reliable way to distinguish Azolla filiculoides Lam. from A. cristata, which was long incorrectly known as A. caroliniana, is to examine the trichomes on the upper surfaces of the leaves. Trichomes are small protuberances that create water resistance. They are unicellular in A. filiculoides, but are septate (two-celled) in A. cristata. Cultivation: This species has been introduced to many regions of the Old World. It is grown for its nitrogen-fixing ability, which can be used to boost the growth rate of water-grown crops such as rice. It can also be removed from lakes and used as green manure. A. filiculoides is frequently cultivated in aquariums and ponds, where it can easily become dominant over other species.
