Description: Perennial plants, mostly less than 30 cm high; corm simple with 2 or 3 lobes (best seen in section), with many dichotomous roots arising from the furrows between the lobes.
Leaves spiral [or 2-ranked], crowded at top of corm, the upper portion terete or flattened, the base expanded and spoon-like and overlapping.
Sporangia embedded in the swollen leaf base, naked or partly or wholly covered by a membranous veil of tissue (velum); megasporangia borne on outer leaves; microsporangia, when present, borne on the inner leaves.
Distribution and occurrence: World: c. 100 species, cosmopolitan except for Pacific islands. Australia: 15 species (14 endemic), all States.
Text by Peter G. Wilson
Taxon concept:
| | Key to the species | |
| 1 | Sporangia naked, not covered by a velum, large and dark brown | Isoetes drummondii |
| Sporangia covered, at least partly, by a velum | Isoetes muelleri |
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