28 American Midland Naturalist Monograph No. 7 



12. Ovary 1-ovuled; fruit 1-seeded; flowers rose-pink, in a 

 spike-like panicle; stipules united to form a cylindri- 

 cal membranous sheath 



Polygonum in 32. Polygonaceae 



12. Ovary with 2 or more ovules: fruit a capsule. 



13. Ovary superior Neobeckia in 18. Cruciferae 



13. Ovary inferior 83. Onagraceae 



7. Leaves opposite or whorled. 

 14. Aquatic monocotyledons. 



15. Perianth 3- or 6-parted ; fruit several-seeded; leaves 5-15 



mm long, minutely spinulose-toothed 



Elodea in 138. Hydrocharitaceae 



15. Perianth none; fruit 1-seeded. 



16. Leaves spinulose-toothed; carpel 1 ...128. Naiadaceae 

 16. Leaves entire; carpels 2-5 ....129. Potamogetonaceae 

 14. Dicotyledons; stamens 4. 



17. Corolla absent or of separate petals 83. Onagraceae 



17. Corolla sympetalous ...Bacopa in 108. Scrophulariaceae 

 2. Leaves, or most of them, deeply lobed or divided. 



18. Leaves finely dissected (or sometimes root-like), often bearing small 

 bladders; flowers (in our species) yellow, bilabiate; fruit a capsule 



112. Lextibulariaceae 



18. Leaves not bladder-bearing, all or most of them finely dissected. 

 19. Flowers white or yellow, solitary. 



20. Floating leaves peltate, narrowly elliptical, 1.5-2 cm long; sub- 

 merged leaves opposite or verticillate; petals 3; sepals 3; 

 pistils 3 4. Cabombaceae 



20. Floating leaves, if any, not peltate. 



21. Leaves alternate; petals 5; sepals 5; pistils more than 3 



Ranunculus in 3. Ranunculaceae 



21. Leaves opposite, the upper lanceolate, serrate; heads soli- 

 tary, radiate; rays 6-10, yellow; achenes 1-1.5 cm long, 

 with 3-6 slender awns Bidens in 125. Compositae 



19. Flowers small, green or whitish. 



22. Flowers green, minute; leaves alternate or whorled. 



23. Leaves simple, entire 86. Hippuridaceae 



23. Leaves not entire. 



24. Leaves all dissected into rather rigid divisions; fruit 1- 



seeded Ceratophyllaceae 



24. Upper leaves sometimes merely pectinate; fruit 4-lobed 



84. Halor.\gaceae 



22. Flowers whitish, whorled at the nodes of the erect, hollow, in- 

 inflated, almost leafless flowering stem; corolla 5-lobed; 

 sepals 5, linear; stamens 5, included; fruit a many-seeded 

 capsule Hottonia in 97. Primulaceae 



Section 12. Trees or Shrubs (Including Woody Climbers) 

 With Opposite or Whorled Leaves 



1. Leaves compound. 

 2. Leaflets 3 or 2. 



3. Stems climbing or trailing. 



