Isoetes - Isoetaceae

Isoetes giessii Launert

Photo: JE. Burrows






Common name



Pseudo-corm 3-lobed; bud scales infrequent, acute, 1.0-2.5 mm long, dark brown, papery. Leaves 10-30, narrowly linear, 0.5-1.0 mm wide apically, gradually widening basally to 3-4 mm near the sporangia. Ligule narrowly triangular, acute, 1.0-1.5 mm long, pale brown. Velum completely enclosing the sporangium. Sporangia subcircular, c. 2.5 mm in diameter. Megaspores of 2 different sizes, ± 0.23 and 0.49 mm in diameter, distal surface pusticulate, usually confluent, with a few convex-sided tubercles prominent, proximal surface with shallow, clearly separated warts in each sector.


giessii: named after J.W.H. Giess (1910-2000), botanist and collector of Namibian plants.


Shallow, sandy, humic substrates overlying granite sheetrock, next to seasonal springs or rivulets, among grasses and herbs; margins of seasonally vlei in arid Acacia scrub.

Distribution worldwide

See African distribution.

Distribution in Africa


Growth form



  • Burrows, J.E. (1990) Southern African Ferns and Fern Allies. Frandsen, Sandton. Page 32. (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 56 - 57. (Includes a picture).
  • 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 9.