[youtube]http://www.youtube.com/watch?v=p9Koqk9iy4E[/youtube]
Azolla sp., the world’s smallest fern, and its nitrogen-fixing symbiont Anabaena azollae. Although small, Azolla is the world’s most important fern economically. It has been used as a fertilizer in the rice paddies of southeastern Asia for centuries.
Pteridology – Little Nitrogen Factories
![Pteridology – Little Nitrogen Factories](https://www.fernsoftheworld.com/wp-content/uploads/2012/09/Azolla.jpg)