Isoetes humilior A.Braun

Aquatic herb; corm 2-lobed, to 5 cm long. Leaves 5–15, spirally arranged, erect, 5–8 cm long, 1–1.5 mm diam., rigid, linear, obtuse, dark green; base to 15 mm wide, winged, whitish; margins often brownish; peripheral fibre strands, internal hairs and stomata absent; trans-lacunar diaphragms not visible; ligule triangular, 1 mm long; labium absent. Sporangia round to elliptic, 3–6 mm long, c. 3 mm wide, translucent, pale; velum opaque, completely covering sporangium, or occasionally with a small, basal, medial sinus exposing the sporangium. Microspores granulose, dark brown. Megaspores Type I, 0.65–0.9 mm diam.; proximal and distal faces shallowly tuberculate to almost smooth, drying whitish to very pale brown.

Occurs in a few subalpine lakes and adjacent rivers, usually in association with Isoetes gunnii .