Isoetes aequinoctialis Welw. ex A.Br.

Rhizomorph trilobed, 4-10 mm in diameter; rhizomorph-scales thin, papery, brownish, often absent. Sporophylls 10-20, more or less trigonous, pale green, stiff, 40-350 x 1-1.5 mm, apex abruptly pointed, with a broad membranous margin (soon disappearing) c. 3 mm wide basally (above sporangia); ligule often trilobed, deltate, attenuate. Sporangium protruding either side of midrib on adaxial side of sporophyll, c. 3-7 x 1.5-3 mm, velum covering lower half of sporangium or reduced to a marginal ring less than 1 mm wide. Megaspores greyish when dry, proximal faces very finely granular or with a central cluster of minute verrucae, distal face with more or less widely spaced papillae or granules, of two sizes, c. 350 µm and 500 µm. Microspores scabrate, 28-40 µm.