Isoetes - Isoetaceae

Isoetes schweinfurthii A. Braun ex Baker






Calamaria schweinfurthii A. Braun ex Baker
Isoetes rhodesiana Alston
Isoetes kersii Wanntorp

Common name


Pseudo-corms 3-lobed; bud scales dark brown to blackish, triangular-cuspidate, ± 6 × 4 mm. Leaves 5-40, narrow, stiff, 150-600 × c.1 mm (at apex) - c.10 mm (around sporangium), broadly winged, apex tapering to a point. Ligule narrowly triangular, sides convex, abruptly pointed, 2-6 mm long, pale, covered by a membranous serrate lip in the lower half. Velum absent or reduced to a vestigial rim. Sporangia 4-12 × 5-9 mm, oblong-obovate to circular. Megaspores 0.4-0.5 mm in diameter, ash-grey to whitish, upper surface almost smooth or with a few tubercles, lower tuberculate with conical warts. Microspores not seen.


I. alstonii is distinguished from I. schweinfurthii by its 2-lobed pseudo-corm. I. schweinfurhii is separated from I. aequinoctialis by lacking a velum.


schweinfurthii: named after Dr Georg August Schweinfurth (1836-1925), German botanical collector and taxonomist.


Shallow seasonally inundated pans in dry deciduous woodland or sometimes in sandy soils overlying sheetrock along river margins.

Distribution worldwide

Africa, Madagascar.

Distribution in Africa

Angola, Benin, Burkina Fasso, Central African Republic, Chad, Ethiopia, Ivory Coast, Kenya, Malawi, Morocco and Western Sahara, Mozambique, Namibia, Senegal, South Africa, Sudan and South Sudan, Tanzania , Zambia, Zimbabwe.

Growth form



  • Burrows, J.E. (1990) Southern African Ferns and Fern Allies. Frandsen, Sandton. Page 36. (Includes a picture).
  • Crouch, N.R., Klopper, R.R., Burrows, J.E. & Burrows, S.M. (2011) Ferns of Southern Africa, A comprehensive guide. Struik Nature. Pages 70 - 71. (Includes a picture).
  • Fisher E. & Lobin W. (2022) The genus Isoetes (Isoetaceae) in Central Africa (DRC, Rwanda, Burundi) with the description of three new species.Willdenowia, 52 Page 316. (Includes a picture).
  • Hedberg, I; Friis, Ib & Persson, E (2009) Lycopodiaceae to Pinaceae.Flora of Ethiopia and Eritrea, vol.1 Pages 18 - 19.
  • Jacobsen, W.B.G. (1983) The Ferns and Fern Allies of Southern Africa. Butterworths, Durban and Pretoria. Pages 153 - 154. (Includes a picture).
  • Roux, J.P. (2001) Conspectus of Southern African Pteridophyta.Southern African Botanical Diversity Network Report, 13 Pages 29 - 30.
  • Roux, J.P. (2009) Synopsis of the Lycopodiophyta and Pteridophyta of Africa, Madagascar and neighbouring islands. Strelitzia 23, South African National Biodiversity Institute, Pretoria. Page 10.
  • Schelpe, E.A.C.L.E. (1970) Pteridophyta.Flora Zambesiaca, 0 Page 30. As Isoetes rhodesiana
  • Verdcourt, B. (2005) Isoetaceae.Flora of Tropical East Africa, Pages 4 - 6.