Ingo Reize (2008)

Azolla cristata

°C
°dKH
Aquarium suitability: yes
Usage: Water surface
Difficulty: easy
Growth: fast
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Synonyms: 
  • Azolla caroliniana auct. non Willd.
  • Azolla mexicana C. Presl

Habit, plant type:

  • free-floating (surface)
  • fern
Botanical name [?]: Azólla cristáta Kaulf.

Major group (unranked): Ferns (Monilophytes)
Order: Salviniales
Family: Azollaceae
Genus: Azolla

Description: 

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 -

References and further reading:
  1. Evrard, C. & Van Hove, C. (2004): Taxonomy of the American Azolla species(Azollaceae): a critical review. - Systematics and Geography of Plants 74: 301-318.
  2. Kasselmann, Christel (2010): Aquarienpflanzen. 3rd edition. DATZ Aquarienbuch, Ulmer Verlag, Stuttgart.
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