Isoetes welwitschii A. Braun
Photo: JE. Burrows
South Africa
Synonyms |
Calamaria welwitschii (A. Braun) Kuntze |
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Common name |
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Description |
Small fern 5–20 cm tall. Pseudo-corm 3(-4)-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, abruptly enlarged to 2-6 mm wide in sporangial area, ± 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 pale or ± dark, suborbicular, up to 2.5-7(-9)× 2-3.5(-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. |
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 | welwitschii: named after the Austrian botanist F. Welwitsch (1806-1872) who first collected this species. |
Habitat | Marshy or perennially wet seepage areas and vleis in grassland, black mud of pools and forest streams, on granite rock. |
Distribution worldwide | Africa, Madagascar. |
Distribution in Africa |
Angola, Botswana, Central African Republic, Dem. Republic of Congo, Eritrea, Ethiopia, Ghana, Kenya, Nigeria, South Africa, Sudan and South Sudan, Tanzania , Zambia. |
Growth form |
Terrestrial. |
Literature |
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