Flora of North America species comparison

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Azollaceae

azolla family, mosquito fern family
Habit Plants aquatic, floating on placid water, occasionally stranded, subsisting on mud; plants heterosporous (producing 2 kinds of spores), leptosporangiate, proliferous by axillary fragmentation.
Roots

translucent to brown, lax, singular [in bundles] without branches, emerging at stem branch points;

root hairs to 1 cm, emerging from root cap.
Stems

usually not green, with extensive subdichotomous branching, prostrate and reniform or polyreniform, or nearly erect.
Leaves

sessile, alternate, often imbricate, in 2 ranks along upper side of stem, 0.6–2 mm wide; each leaf with 2 lobes;

upper (emersed) lobe greenish or reddish and photosynthetic, with narrow colorless margin, several cells thick, bearing colony of blue-green algae (Anabaena) in ovoid cavity at base of lower side;

lower lobe often floating or immersed, slightly larger than upper lobe, mostly not green (often colorless and translucent), 1 cell thick except at base, ± cup-shaped.
Sporocarps

in pairs [tetrads] at base of lateral branches, members of pair of same sex or of different sexes.
Megasporocarps

containing 1 megasporangium that produces 1 functional megaspore.
Megaspore

spheric, 0.2–0.6 mm, topped with dark, conic, slightly narrower structure (indusium) covering 3 [9] floats and a blue-green algal colony.
Microsporocarps

globose, apically umbonate, 10–27µm diam., containing to 130 microsporangia;

microsporangia containing 32 or 64 microspores 3 µm diam., aggregated into 3–10 masses covered with arrowlike barbs [glabrous or with needlelike hairs on 1 side].

Azollaceae
Distribution
Worldwide; tropical to temperate regions
Discussion

Azollaceae has been included in Salviniaceae, but the relationship is not close.

In this treatment, "upper lobe" refers to the emersed lobe and "lower lobe" refers to the immersed lobe. Developmentally, the emersed lobe is actually abaxial and the immersed lobe is adaxial. To facilitate identification in the field, however, the terms describe the appearance of the lobes to the viewer, not the development of the lobes.

Genus 1, species ca. 7 (3 species in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Parent taxa
Subordinate taxa
Name authority Wettstein
Source FNA vol. 2, p. 338. Treatment author: Thomas A. Lumpkin.
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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