Small, floating herbs, often forming a mat over still waters, rhizome fine, horizontal, branching alternately to the left and right, bearing small, close leaves and fine, simple roots, protostelic. Leaves +/- imbricate, alternate, bilobed, papillose. Sporangia borne in sporocarps, in the axils of the submerged lobes of the leaves, enclosed in a thin indusium, the sporocarps of 2 types, microsporocarp large, with several microsporangia each with many microspores, megasporocarp with a single megasporangium with a single megaspore; spores globose, trilete.
A mongeneric family with about 6 species, found throughout the tropical and temperate regions of the world. Azolla pinnata is the only, and possibly introduced species in Papuasia.
Croft, J.R. 1985. Azollaceae. In Leach, G.J. & Osborne, P.L., Fresh water plants of Papua New Guinea. Univ. P.N.G., Port Moresby. pp. 36 - 38.
Follieri, M. 1977. Classification and phyllogeny of living and fossil water ferns of the genus "Azolla". Webbia 31: 97 - 104, f. pl. 1 - 2.
Johns, R.J. 1981. The ferns and fern-allies of Papua New Guinea. Part twelve: the Azollaceae. P.N.G. Univ. Tech. Res. Rep. R 48 - 81: 35.1 - 35.3
Lumpkin, T.A. & Plucknett, D.L. 1980. Azolla: botany, physiology, and use as a green manure. Econ. Bot. 34: 111 - 153, f. 1 - 20.
Moore, A.W. 1969. Azolla: biology and agronomic significance. Bot. Rev. 34: 17 - 34.
Sweet, A. & Hills, L.V 1971. A study of Azolla pinnata R. Brown. Amer. Fern J. 71: 1 - 13, pl. 1 - 4.
Genera in Australia and Papuasia
|A family of a single genus ...||Azolla (1)|
For convenience, some authors place both Azolla and Salvinia in the Salviniaceae, but there are substantial differences between the two families.
Updated November 1999 by Jim Croft (email@example.com)