Azolla cristata

In most cases, Azolla cristata has been called "Azolla caroliniana" in the hobby as well as in botanical literature. However, accoring to recent research, A. caroliniana is a synonym for Azolla filiculoides .

The very similar, easily-confused species A. cristata and A. filiculoides can best be discerned by microscopical characteristics of the female spores (megaspores). However, there are also some other distinguishing characteristics:

Azolla cristata:
- the hairs on the upper side of the floating leaves consist of 2 or, less frequently, 3 cells (microscope!).
- The upper lobe of the floating leaf is almost sharp-tipped, with a narrow unpigmented membraneous margin (magnifying glass!).
- The sprouts have a more compact growth habit and lie flat on the water surface.

Azolla filiculoides:
- The hairs on the upper side of the floating leaf consist of a single cell (mikroscope!).
- The upper lobe of the floating leaf is obtuse, with a relatively wide unpigmented membraneous margin (magnifying glass!).
- The sprouts grow more loosely, the shoot tips grow out of the water in most cases.


- To be continued -