Flora of North America species comparison

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Azolla filiculoides

Azollaceae

duckweed fern, large mosquito fern, mosquito fern, Pacific mosquito fern, water fern

azolla family, mosquito fern family
Habit Plants green to yellowish green or dark red, with 2 growth stages; plants fertile only in mature stage, generally in late spring. 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

prostrate when immature, 1–3 cm, internodes elongate to 5 mm, becoming nearly erect to 5 cm or more when mature and crowded.

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.
Hairs

on upper leaf lobes strictly unicellular.

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(s)

warty with raised angular bumps, each with a tangle of filaments.

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].

Azolla filiculoides

Azollaceae
Habitat Stagnant and slow-moving waters.
Distribution
from FNA
AZ; CA; OR; WA; BC; Mexico; Central America; Europe; ne Asia; s Africa; Pacific Islands in Hawaii
[WildflowerSearch map]
[BONAP county map]
Worldwide; tropical to temperate regions
Discussion

Azolla filiculoides is cold tolerant, surviving even in fragmented parts under thin ice. It usually reaches a climax population in late spring, becomes fertile, collapses, and is replaced by other more heat-tolerant aquatics such as Lemna spp. Hybrids between this species (male) and A. microphylla Kaulfuss (female), a species of Central America, South America, and the West Indies, have been reported (Do V. C. et al. 1989). V. M. Bates and E. T. Browne (1981) reported A. filiculoides from Georgia, far removed from its main range in western North America. The most likely explanation is that the plants represent escapes from horticulture.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.)
Source FNA vol. 2, p. 341. FNA vol. 2, p. 338. Author: Thomas A. Lumpkin.
Parent taxa Azollaceae > Azolla
Sibling taxa
A. caroliniana, A. mexicana
Subordinate taxa
Name authority Lamarck: in Lamarck et al., Encycl. 1: 343. (1783) Wettstein
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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