Isoetes welwitschii A. braun

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Synonyms: Calamaria natalensis (Baker) Kuntze
Calamaria welwitschii (A. Braun) Kuntze
Isoetes natalensis Baker
Common names:
Status: Native
Small herb 5–20 cm tall. Pseudo-corm 3-lobed, scarcely developed or up to 1.5 cm wide; bud scales dark brown to black, triangular with the tip abruptly narrowed to a sharp point, up to 3 × 7 mm. Leaves 5-35, pale green, erect, slender, 50-350 mm × 4 mm at the base, ± semi-circular in cross-section, apex awl-shaped. Dried specimens often rather distinctly bicolored, whitish at base (sporangial part and about 1.5 cm above it) contrasting with dark green upper parts. Ligule narrowly triangular, 2.5 mm long. Velum absent or rarely a rim ± 1 mm wide. Sporangia suborbicular, up to 2.5 (-9)× 2 (-5) mm. Megaspores of two sizes, about 0.45-0.56 mm in diameter, ash grey to white, distal surface tuberculate with smaller warts interspaced, proximal surface trilete with spaced tubercles confined to the centre or if more extensive then central ones the largest or sometimes ± smooth. Microspores minutely tuberculate.
Type location:
Notes: Similar to I. schweinfurthii in which the warts on the distal face of the megaspores have concave sides which flare out at the base.
Derivation of specific name: welwitschii: named after the Austrian botanist F. Welwitsch (1806-1872) who first collected this species.
Habitat: Marshy or perennially wet seepage area.
Altitude range: 1200 - 1700 m
Worldwide distribution: Angola, Botswana, Central African Republic, Eritrea, Ethiopia, Ghana, Kenya, Madagascar, Nigeria, South Africa, Sudan, Tanzania, Zambia.
Zambian distribution (Flora Zambesiaca):
Zambian distribution (Provinces):
Growth form(s): Terrestrial.
Endemic status:
Red data list status:
Insects associated with this species:
Spot characters: Display spot characters for this species

Burrows, J.E. (1990). Southern African Ferns and Fern Allies. Frandsen, Sandton. Pages 34 - 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 68 - 69. (Includes a picture).

Jacobsen, W.B.G. (1983). The Ferns and Fern Allies of Southern Africa. Butterworths, Durban and Pretoria. Page 154.

Roux, J.P. (2001). Conspectus of Southern African Pteridophyta. Southern African Botanical Diversity Network Report 13 Page 30.

Roux, J.P. (2009). Synopsis of the Lycopodiophyta and Pteridophyta of Africa, Madagascar and neighbouring islands Page 11.

Other sources of information about Isoetes welwitschii:

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Flora of Botswana: Isoetes welwitschii

External websites:

African Plants: A Photo Guide (Senckenberg): Isoetes welwitschii
BHL (Biodiversity Heritage Library): Isoetes welwitschii
EOL (Encyclopedia of Life): Isoetes welwitschii
GBIF (Global Biodiversity Information Facility): Isoetes welwitschii
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IPNI (International Plant Names Index): Isoetes welwitschii
JSTOR Plant Science: Isoetes welwitschii
Mansfeld World Database of Agricultural and Horticultural Crops: Isoetes welwitschii
Plants of the World Online: Isoetes welwitschii
Tropicos: Isoetes welwitschii
Wikipedia: Isoetes welwitschii

Copyright: Mike Bingham, Annette Willemen, Bart Wursten, Petra Ballings and Mark Hyde, 2011-24

Bingham, M.G., Willemen, A., Wursten, B.T., Ballings, P. and Hyde, M.A. (2024). Flora of Zambia: Species information: Isoetes welwitschii., retrieved 23 April 2024

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