Isoetes - Isoetaceae

Isoetes aequinoctialis Welw. ex A. Braun

Photo: JE. Burrows
Zimbabwe

Photo: JE. Burrows
Zimbabwe

 

 

 

 

Synonyms

Calamaria aequinoctialis (Welw. ex A.Braun) Kuntze
Isoetes erongensis Wanntorp

Common name

Description

Pseudo-corm 3-lobed, 5-10 mm in diameter; bud scales brownish, thin, papery, often absent. Leaves 10-20, pale green, stiff, 40-350 mm × 1-1.5 mm, apex abruptly pointed, triangular in cross-section, initially with broad membranous margin about 3 mm wide above the sporangia. Ligule often 3-lobed, deltate, tapering to a point. Velum covering lower half of the sporangia or reduced to a marginal ring less than 1-2 mm wide. Sporangia 3-7 × 1.5-3 mm. Megaspores of two sizes, about 0.5 and 0.35 mm, greyish when dry, upper face finely granular or minutely verrucose, lower with widely spaced papillae or granules. Micropsores scabrate.

Notes

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

Derivation

aequinoctialis: of the equinox, a term used for flowers that open or close at stated hours. Obscure reference, it may refer to the time of year when this plant was first collected in Angola by F.M.J. Welwitsch.

Habitat

In perennial streams and seasonally waterlogged sites overlying granite sheetrock, boggy grassland.

Distribution worldwide

See African distribution.

Distribution in Africa

Angola, Ghana, Mali, Namibia, South Africa, Tanzania , Zambia, Zimbabwe.

Growth form

Terrestrial.

Literature

  • Burrows, J.E. (1990) Southern African Ferns and Fern Allies. Frandsen, Sandton. Pages 33 - 34. (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 66 - 67. (Includes a picture).
  • Jacobsen, W.B.G. (1983) The Ferns and Fern Allies of Southern Africa. Butterworths, Durban and Pretoria. Pages 155 - 156. (Includes a picture).
  • Kornas, J. (1979) Distribution and ecology of the Pteridophytes in Zambia. Polska Akademia Nauk Wydzial II Nauk Biologicznych. Pages 34 - 35.
  • Roux, J.P. (2001) Conspectus of Southern African Pteridophyta. Southern African Botanical Diversity Network Report, 13 Page 29.
  • 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 8.
  • Schelpe, E.A.C.L.E. (1970) Pteridophyta. Flora Zambesiaca, 0 Pages 30 - 32.
  • Verdcourt, B. (2005) Isoetaceae. Flora of Tropical East Africa, Pages 2 - 3.
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