Lemnaceae

This specialised family of aquatic plants is cosmopolitan. In Australia, the tiny plants may be found floating anywhere still, fresh, nutrient-rich water is found.

Characteristic features of the family Lemnaceae in Australia include:

• tiny, floating or submerged plants comprising one or more flattened or globose, green, leaf-like thalli, with or without roots, sometimes forming large rafts on the water surface.
  
• flowers unisexual, rarely seen, borne in pockets on the thallus, each pocket with two male and one female flowers, without perianths
  
• fruit a tiny, indehiscent nut

Description

Perennial aquatic herbs, free-floating at or below the water surface. Perennating by dormant thalli or turions (a short, condensed shoot, filled with starch). Vegetative reproduction by budding. Internal secretions not obvious. Plants thalloid, lacking recognisable stems or leaves, glabrous. Male and female flowers occurring on the same plant. Flowers rarely produced, occurring in 2 marginal pouches; the inflorescence consisting either of 2 (-3) male flowers and one female flower or one male flower and one female flower. Spathes present or absent. Bracts and bracteoles absent. Pollination by insects. Flowers odourless; sessile. Floral disc absent; nectaries absent. Perianth vestigial or absent. Fertile stamens 1–2, free of the perianth, free of the ovary and style, distinct from each other, all ±equal. Anthers basifixed, not versatile, opening sideways or terminally by longitudinal slits or by transverse slits, 1–2-celled. Ovary superior and sessile. Carpel 1; ovary with 1 locule. Style terminal, single and unbranched. Ovules 1 (2–7), sessile; placentation basal. Fruit a dry, dehiscent or indehiscent utricle. Disseminule micro-surface ±smooth, costate or reticulate, white, cream or brown; dull. Seeds 1 (2–5) per fruit. Aril absent. Cotyledons 1. Embryo straight.
(Note: this description has been generated from the coded data compiled for the key. Any errors in the key data will be reflected in the descriptions.)

A treatment of the family Lemnaceae has not yet been published in the Flora of Australia. It will appear in Volume 39.

Australian genera of Lemnaceae (as recognised for the Flora of Australia)

Lemna
Spirodela
Wolffia