Flora of North America species comparison

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Azolla mexicana

Azolla filiculoides

Mexican mosquito fern

duckweed fern, large mosquito fern, mosquito fern, Pacific mosquito fern, water fern
Habit Plants green or often blue-green to dark red, some red-fringed leaves usually present in nature, free-floating or forming a multilayer mat to 4 cm thick in early summer; plants frequently fertile. Plants green to yellowish green or dark red, with 2 growth stages; plants fertile only in mature stage, generally in late spring.
Stems

prostrate, 1–1.5 cm.

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

hairs on upper leaf lobe near stem 2(–3)-celled;

broad pedicel cell often 1/2 or more height of hair, apical cell curved, with tip nearly parallel to leaf surface.

Megaspores

not covered with raised angular bumps, pitted and sparsely covered with a few long filaments extending over surface.

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

on upper leaf lobes strictly unicellular.

Azolla mexicana

Azolla filiculoides
Habitat Stagnant or slow-moving waters. Stagnant and slow-moving waters.
Distribution
from FNA
AR; AZ; CA; CO; IA; IL; KS; MN; MO; NE; NM; NV; OK; OR; UT; WA; WI; BC; Mexico; Central America; South America
from FNA
AZ; CA; OR; WA; BC; Mexico; Central America; Europe; ne Asia; s Africa; Pacific Islands in Hawaii
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[BONAP county map]
Discussion

Azolla mexicana is generally less cold tolerant and has a narrower environmental range than A. caroliniana. Both species are closely related and are similar vegetatively in culture. In the western United States, A. mexicana is often fertile. Distribution in the Great Plains area is tentative and needs further study. In the eastern United States, A. mexicana may have been occasionally introduced.

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

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.)
Source FNA vol. 2, p. 341. FNA vol. 2, p. 341.
Parent taxa Azollaceae > Azolla Azollaceae > Azolla
Sibling taxa
A. caroliniana, A. filiculoides
A. caroliniana, A. mexicana
Name authority C. Presl: Abh. Königl. Böhm. Ges. Wiss. ser. 5, 3: 150. (1845) Lamarck: in Lamarck et al., Encycl. 1: 343. (1783)
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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