Small floating ferns, whole plant oblong to deltoid in outline, up to 20 × 15 mm. Rhizome up to 0.2 mm in diameter, horizontal, branched into 3-5 alternate pinnae. Roots single or in fascicles of 2-3 at the branche nodes, up to 3.5 cm long, hairy, with conspicuous root cap. Leaves minute in 2 rows, dark green, 2-lobed; upper lobe up to 1.1 mm long, ovate to broadly elliptic in outline, apex pointed, papillate in the centre and with a hyaline border; lower lobe colourless, more or less equal in size. Plant heterosporous, sporocarps on the submerged lower lobes of the leaves.
Derivation of specific name: pinnata: with pinnate leaves, refers to the distinctly pinnate arrangements of the branches of the stem.
Habitat: Forms dense mats on shallow water or lakes, ponds and backwaters of rivers.
Worldwide distribution: South Africa, southern Mozambique, northern parts of Namibia & Botswana & Zimbabwe; widespread throughout tropical africa; also Madagascar, New Guinea, Australia.
Burrows, J.E. (1990). Southern African Ferns and Fern Allies. Frandsen, Sandton. Pages 81 - 82. (Includes a picture).
Burrows, J.E. & Burrows, S.M. (1993). An annotated check-list of the pteridophytes of Malawi Kirkia 14(1) Page 83. As Azolla pinnata R.Br.
Crouch, N.R., Klopper, R.R., Burrows, J.E. & Burrows, S.M. (2011). Ferns of Southern Africa, A comprehensive guide Struik Nature Pages 212 - 214. (Includes a picture).
Jacobsen, W.B.G. (1983). The Ferns and Fern Allies of Southern Africa. Butterworths, Durban and Pretoria. Pages 493 - 494. (Includes a picture).
Kornas, J. (1979). Distribution and ecology of the Pteridophytes in Zambia Polska Akademia Nauk Wydzial II Nauk Biologicznych Page 123.
Roux, J.P. (2009). Synopsis of the Lycopodiophyta and Pteridophyta of Africa, Madagascar and neighbouring islands Page 59.
Schelpe, E.A.C.L.E. (1970). Pteridophyta Flora Zambesiaca Pages 69 - 70.
Hyde, M.A., Wursten, B.T., Ballings, P. & Coates Palgrave, M. (2019). Flora of Botswana: Species information: Azolla pinnata subsp. africana.