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FNA | Family List | FNA Vol. 2 | Azollaceae | Azolla

3. Azolla filiculoides Lamarck in Lamarck et al., Encycl. 1: 343. 1783.

Plants green to yellowish green or dark red, with 2 growth stages; plants fertile only in mature stage, generally in late spring. Stems prostrate when immature, 1--3 cm, internodes elongate to 5 mm, becoming nearly erect to 5 cm or more when mature and crowded. Hairs on upper leaf lobes strictly unicellular. Megaspores warty with raised angular bumps, each with a tangle of filaments.

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.


Bates, V. M. and E. T. Browne. 1981. Azolla filiculoides new to the southeastern United States. Amer. Fern J. 71: 33--34. Duncan, R. E. 1940. The cytology of sporangium development in Azolla filiculoides. Bull. Torrey Bot. Club 67: 391--412.

1 (1) Largest hairs on upper leaf lobe unicellular; megaspores warty with raised angular bumps. 3. Azolla filiculoides   (1)
+ Largest hairs on upper leaf lobe with 2 or more cells; megaspores not covered with raised angular bumps.   (2)
2 (2) Megaspores not pitted, densely covered with tangled filaments (filosum). 1. Azolla caroliniana   (2)
+ Megaspores pitted, sparsely covered with a few long filaments (filosum). 2. Azolla mexicana   (1)


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