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2 Leaf blades oval in shape, ca. 1.5-2× as long as wide, at maturity floating on the water’s surface; underwater portions of fresh plant coated in transparent mucilage |
2 Leaf blades orbicular in shape, ca. 1× as long as wide, at maturity floating on the water’s surface, emersed, or submersed; underwater portions of fresh plant not mucilaginous (though possibly with green algae, etc.). |
3 Leaves small, < 8 cm in diameter, at maturity emersed or submersed |
3 Leaves large, > 20 cm in diameter, at maturity floating on the water’s surface or emersed |
1 Leaves not peltate, the petiole attached at a cuneate, cordate, or sagittate base. |
4 Leaf blades cuneate, rounded, or truncate at the base. |
5 Basal leaves lanceolate, 3-6 mm long |
5 Basal leaves variously shaped, > 10 mm long. |
6 Main veins palmate from the leaf base and also diverging from the midvein, the secondary and tertiary veins then reticulating; inflorescence a spike; [ Eudicots] |
6 Main veins either parallel or palmate from the leaf base with cross-veins at nearly right angles to the main veins; inflorescence either a diffuse raceme or panicle of white flowers, or a linear spadix of tightly packed golden-yellow flowers; [ Monocots]. |
7 Inflorescence diffuse, a raceme or panicle with whorled branches or pedicels, the flowers widely spaced and white; leaves green, “wettable” |
7 Inflorescence tightly packed with flowers, an elongate, golden yellow spadix; leaves blue-green, “unwettable” |
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8 Leaf blades sagittate, the two lobes distinctly acute; leaf apex acute; leaf blade 1.3-3× as long as wide |
8 Leaf blades cordate, the two lobes rounded or sub- acute; leaf apex rounded or apiculate; leaf blade 0.8-8× as long as wide. |
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10 Flowers 4-5 -merous ( sepals 4-5, petals 4-5, stamens 4-5); [ Eudicots] |
11 Leaves emersed or submersed, on stout, stiff petioles (the submersed and winter leaves cuneate-based and lanceolate); flowers 4 -merous ( sepals 4, petals 4, stamens 4); inflorescence a spike |
11 Leaves floating, on slender, flexuous petioles (all leaves cordate-based); flowers 5 -merous ( sepals 5, petals 5, stamens 5); inflorescence an umbel |
10 Flowers 3 -merous or many (>5-) -merous; [ Basal Angiosperms or Monocots]. |
12 Perianth parts numerous (usually showing differentiation into sepals and petals, though often with some intergradation), borne in a spiral; stamens numerous; leaves usually > 10 cm long or > 10 cm wide, or both (a few northern species of Nymphaea with leaves as small as 2.5 cm × 2.5 cm); [ Basal Angiosperms] |
12 Perianth parts 3-6 (either differentiated or not into sepals and petals); stamens either 3, or 9-12 (-18), or >20; leaves 1-10 cm long, 1-10 cm wide; [ Monocots]. |
13 Perianth strongly differentiated, the 3 sepals green, leathery, and persistent, the 3 petals yellow or white, delicate, deciduous; stamens 20 or more |
13 Perianth not strongly differentiated, the sepals petaloid and similar in texture and color to the petals; stamens 10 or fewer. |
14 Flowers unisexual, white, the sepals and petals separate; stamens 3, 6, 9, 12, 15, or 18; leaves either with a central area of spongiform cells (most easily seen on the lower leaf surface) ( Limnobium), or without spongiform cells ( Ottelia) |
14 Flowers bisexual, white to blue, the perianth segments united below into a perianth tube 3-45 mm long; stamens 3; leaves lacking a central area of spongiform cells |