A N F Keys
1 Plants with adventitious roots, floating on surface of water
2 Plants with a basal rosettes having spreading to ascending leaves with conspicuous, raised veins and densely covered with velveteen, water-repellent hairs .. Pistia stratiotes [pics]
2' Plant with leaves (fronds) floating on water, venation inconspicuous (observe with magnification), glabrous .. Lemna
1' Plants lacking adventitious roots, floating just beneath the surface of the water; tightly rosetted of 1−2(−4) highly reduced green shoots (fronds), with daughter frond arising from a basal pouch .. Wolffiella lingulata
1 Fronds hemi-spheroid with inflated lower surface, lower surface grayish green but sometimes tinged purplish red, large blisters on surface to 2.5 mm long, convex surface with sculpturing of cell walls .. Lemna gibba [pics]
1' Fronds ± flat and not inflated, lower surface green like upper surface and lacking blisters
2 Frond at maturity obovate, 2.5−3.5 × 2−2.7 mm, green often senescing colorless, somewhat biconvex with expansion more on lower surface, broadly acute at tip, mostly 3-veined (view on colorless, senescent frond), commonly with 1 vein very close to margin .. Lemna minor [pics]
2' Fronds at maturity obovate to ± broadly elliptic, 0.8−4 × 0.5−2 mm, green often senescing colorless, surfaces flat, obtuse at tip, indistinctly 1-veined with vein rarely extending beyond midfrond .. Lemna minuta [pics]
The text of the above keys used with permission from
A Naturalist's Flora of the Santa Monica Mountains and Simi Hills, California
© Copyright
Barry A. Prigge and Arthur C. Gibson
2013