Isoetes philippinensis Merr. & L.M.Perry

Submerged aquatic. Stock apparently 3-4-lobed. Leaves numerous, elongate, up to 50 cm, slender, rather fiaccid, 3 mm broad in the middle, c. 7 mm broad at base, with membranaeeous wings. Accessory peripheral strands wanting. Foveae 3-4 cm long, narrow, 1.5-2 mm broad, gradually narrowed upwards, with hyaline margins. Velum none. Ligule elongate, ovate-triangular. Sporangia oblong, c. 9 by 3 mm, pale. Megaspores above 420 μ in diam. with a prominent triradiate marking, usually smooth on the inner surfaces, sometimes sparingly and minutely rugose; reticulate on the outer surface. Microspores 25-30 by c. 22 μ, very minutely scabrous.

It is a tropical plant. In Mindanao it grows in streams between 400-500 m above sea level.