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Roots absent. Fronds floating or submersed (only turions sink to bottom), 1 or 2, coherent, each frond globular, ovoid, or boat-shaped, 3-dimensional, smaller than 1.6 mm, margins entire; air spaces not in tissue; reproductive cavity terminal, at base from which daughter fronds (but no flowers) originate, conic, lower side of cavity with short tract of elongated cells along median line forming connection between node and attachment to mother frond; veins 0; scale at base of frond absent; anthocyanins absent; in some species pigment cells present (visible in dead fronds as brown dots); turions light green, globular, smaller than growing fronds. Flowers 1 per frond, originating in cavity ± on median line of upper frond surface, not surrounded by utricular scale; stamen 1, 2-locular. Seeds 1, nearly smooth. x = 10, 20, 21, 22, 23.
Fronds free floating on or beneath water surface, 1 or 2 coherent together, green on upper surface, green to transparent on lower surface, never reddish, symmetric, globose, ovoid, or boat-shaped, with 1 basal cavity reproducing daughter fronds, cavity not surrounded by a scale at base; veins absent. Pigment cells (in our species) absent in vegetative cells. Roots absent. Daughter fronds connected to mother frond by a very short stipe (not visible). Flower emerging from a cavity near median line of upper surface, not surrounded by a scale; ovary with 1 ovule; stamen 1, 2-locular. Seed 1, subsmooth.
Thallus minute, not over ca 1.5 mm, thickened, globose to ellipsoid or ovoid, or flattened on the upper side only, without veins or roots; reproductive pouch solitary, on the upper surface near the basal end, to one side of the midline; reproduction almost entirely by budding, the young plants soon detached; fls (rarely produced) without a spathe, paired, one of each sex, the pistillate one nearer the base, with a single orthotropous ovule; anther unilocular, opening across the top. 8, cosmop. The smallest angiosperm.
Fronds floating on or just below water surface, 1 or 2 cohering together, globular, ovoid, cylindric or boat-shaped; daughter fronds originating at frond base in terminal conical cavity; air spaces absent. Turions present under unfavourable conditions, small, globular, whitish green. Flower cavity near median line of upper surface.
Minute free-floating aquatics. Thallus almost ellipsoid, ± 1 mm. in diameter, flattened on the upper surface at water-level. Daughter thallus produced in a circular lateral pit, soon separating from parent. Roots absent. Flowers in a pit on the upper surface of the median line, 1 staminate, 1 pistillate; spathe absent.
Fronds minute, thick, globular, without roots. Spadix of 1 staminate and 1 pistillate flower, bursting through the tissues of the upper surface of the frond, without a spathe.
