22 American Midland Naturalist Monograph No. 2 



10. Stamens distinct; flowers cymose 128. Apocynaceae 



10. Filaments united into a tube enclosing the pistil, the anthers adnate 



to the stigma, and the pollen cohering in masses 



129. ASCLEPIADACEAE 



9. Plants with watery juice; seeds without hairs. 



11. Sepals 4, petal-like; petals 0; stamens numerous; style persistent on 



the achene, often pubescent Clemaiis in 62. Ranunculus 



1 1 . Perianth 6-parted; stamens 6; flowers dioecious; fruit a 3-angled 



capsule 32. DiOSCOREACEAE 



8. Leaves toothed or lobed. 



12. Leaves triangular-hastate; flowers pink, in small heads 



MHiania in 152. CoMPOSITAE 



12. Leaves not triangular-hastate; flowers green, dioecious, in catkins or 



panicles 45. Cannabinaceae 



7. Leaves alternate, or reduced to inconspicuous scales. 



13. Plants with chlorophyll, not parasitic; leayes not reduced to scales. 



14. Leaves with sheathing stipules; corolla none; calyx 5-lobed; flowers 



perfect; fruit an achene 50. PoLYGONACEAE 



14. Leaves without sheathing stipules. 



15. Flowers dioecious; perianth 6-parted; stamens 6. 



16. Flowers in drooping racemes or panicles; styles 3, distinct; 

 fruit a 3-angled or -winged capsule 32. DiOSCOREACEAE 



16. Flowers in umbels; stigmas thick, almost sessile; fruit a small 



bluish black berry Smilax in 31. LiLIACEAE 



15. Flowers perfect; corolla sympetalous; stamens 5. 



17. Corolla funnelform; fruit a capsule; plants often with milky 



juice 130. Convolvulaceae 



17. Corolla rotate, purple or blue (or white); anthers yellow, con- 

 nivent around the style, opening by apical pores; berries red; 



juice watery Solatium dulcamara in 136. SoLANACEAE 



13. Plants bright yellow or orange, parasitic on other plants and lacking chlor- 

 ophyll; leaves reduced to scales; fruit a capsule 



Cuscuta in 1 30. CoNVOLVULACEAE 



Section H. Aquatic Plants, Floating on or Submerged in Water 



Plants very small, free-floating, thalloid, without stems and leaves 25. LemNACEAE 



, Plants larger, normally with leaves and usually with stems. 

 2. Leaves entire or finely toothed. 



3. Blades deeply cordate at the base; flowers large, solitary 64. NymphaEACEAE 



3. Blades not deeply cordate, or peltate. 



4. Floating leaves spatulate; leaves opposite, small; flowers minute, monoecious, 

 sessile, 1-3 in the axils; stamen 1; styles 2, filiform; fruit 4-lobed, notched 



at the apex 93. Callitrichaceae 



4. Leaves never spatulate. 



5. Plants acaulescent; leaves long, linear; fertile flowers on long, slender 



scapes; fruit many-seeded Vallisneria in 21. Hydrocharitaceae 



5. Plants with stems. 



6. Leaves alternate or imperfectly opposite. 



7. Flowers green, in si)ikes ; sepals 4; stamens 4; carpels usually 4; 

 stipules present, membranous; fruit 1 -seeded.. 18. PoTAMOGETONACEAE 

 7. Flowers not green. 



8. Flowers blue, white, or yellow, solitary; stipules none; fruit many- 

 seeded Heteranthera in 29. PoNTEDERIACEAE 



8. Flowers rose-pink, in spike-like racemes; stipules united to form a 



cylindrical, membranous sheath; fruit 1 -seeded species of 



Pohgomim in 50. Polygonaceae 



6. Leaves opposite or whorled. 



