Flora of North America species comparison

7–21, to 3 cm, 1 or 2 perforating scale.

(1–)2–21 per frond, abaxial surface at node.

ovaries 1–2-ovulate.

1(–2) per frond, surrounded by small utricular, membranous scale;

stamens 2, 4-locular.

1–1.5 mm, laterally winged to apex.

with 12–20 distinct ribs.

1–3, longitudinally ribbed.

obovate to circular, flat or rarely gibbous, 2–10 mm, 1–1.5 times as long as wide, apex rounded or pointed, upper surface sometimes with red spot in center;

veins 7–16(–21);

turions sometimes present, rootless, brownish olive, circular-reniform, 1–2 mm diam.

floating (only turions sink to bottom), 2–10, coherent in groups, each obovate-circular, flat or gibbous, 1.5–10 mm, margins entire;

air spaces in tissue;

reproductive pouches 2, lateral, at base from which daughter fronds and flowers originate, triangular;

veins (3–)5–16(–21), from point in proximal part of frond (node); small bifid 2-cleft membranous scale (interpreted as prophyllum) enveloping base of frond, covering point of attachment of roots;

anthocyanins present (especially on abaxial surface);

pigment cells present (visible in dead fronds as brown dots);

turions present or absent, brownish olive, circular-reniform, smaller than growing frond.

= 10, 18, 23.

= 30, 38, 40, 50, 80.