Isoetes alstonii C.F.Reed & Verdc.

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Isoetes alstonii

Picture: Petra Ballings

Isoetes alstonii

Picture: Petra Ballings

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Common names:
Status: Native
Pseudo-corm 10-20 cm in diameter, 2-lobed; bud scales vestigial or lacking. Leaves 10-40, linear, 130-400 mm × 1 mm (apically)- 6 mm (at base),apex tapering to a point, yellow to midgreen, semi-circular in cross-section, abruptly ovate-oblong at the base, with broadly hyaline wing, stomata present in upper parts of the leaves. Ligule 1-2 × c. 1.5 mm, hyaline, triangular, pointed. Velum very narrow, reduced to a thin marginal ring. Sporangia 4-10 × 3-6 mm. Megaspores of 2 sizes, 0.52 and 0.3 mm in diameter, dark grey, drying white, usually 3-radiate, with large warts below, granulated above.
Type location:
Isotype from Zimbabwe, Victoria Falls
Notes: Incorrectly located in N by Schelpe 1970 (Kornas, 1979).
I. alstonii is distinguished from other species in our region by its 2-lobed pseudo-corm and a sporangium that is blackish when wet.
Derivation of specific name: alstonii: named after A.H.G. Alston (1902-1958), Britisch botanist specialised in African pteridophytes.
Habitat: Aquatic plant found in permanent water, at the edges of pools, in seasonally dry streambeds and pools, perannial in permanent mist spray of the Victoria Falls.
Altitude range: 880 - 1100 m
Worldwide distribution: Ethiopia, Mozambique, Namibia, Tanzania, Zambia, Zimbabwe.
Zambian distribution (Flora Zambesiaca): N,W,C,S
Zambian distribution (Provinces): Nw,C,S
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 36 - 37. (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 72 - 73. (Includes a picture).

Jacobsen, W.B.G. (1983). The Ferns and Fern Allies of Southern Africa. Butterworths, Durban and Pretoria. Pages 154 - 155. (Includes a picture).

Kornas, J. (1979). Distribution and ecology of the Pteridophytes in Zambia Polska Akademia Nauk Wydzial II Nauk Biologicznych Page 35.

Reed, C.F. & Verdcourt, B. (1965). Isoetes alstonii, a new species of Isoetes from Rhodesia Kirkia 5(1) Pages 19 - 20. Protologue (Includes a picture).

Roux, J.P. (2009). Synopsis of the Lycopodiophyta and Pteridophyta of Africa, Madagascar and neighbouring islands Page 8.

Schelpe, E.A.C.L.E. (1970). Pteridophyta Flora Zambesiaca Page 30. (Includes a picture).

Other sources of information about Isoetes alstonii:

Our websites:

Flora of Mozambique: Isoetes alstonii
Flora of Zimbabwe: Isoetes alstonii

External websites:

African Plants: A Photo Guide (Senckenberg): Isoetes alstonii
BHL (Biodiversity Heritage Library): Isoetes alstonii
EOL (Encyclopedia of Life): Isoetes alstonii
ePIC (electronic Plant Information Center): Isoetes alstonii
Flora Zambesiaca web site: Isoetes alstonii
GBIF (Global Biodiversity Information Facility): Isoetes alstonii
Google: Web - Images - Scholar
GRIN (Germplasm Resources Information Network): Isoetes alstonii
iNaturalist: Isoetes alstonii
IPNI (International Plant Names Index): Isoetes alstonii
JSTOR Plant Science: Isoetes alstonii
Kew Herbarium catalogue: Isoetes alstonii
Mansfeld World Database of Agricultural and Horticultural Crops: Isoetes alstonii
Plants of the World Online: Isoetes alstonii
Tropicos: Isoetes alstonii
Wikipedia: Isoetes alstonii

Copyright: Mike Bingham, Annette Willemen, Bart Wursten, Petra Ballings and Mark Hyde, 2011-21

Bingham, M.G., Willemen, A., Wursten, B.T., Ballings, P. and Hyde, M.A. (2021). Flora of Zambia: Species information: Isoetes alstonii., retrieved 27 November 2021

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