278 American Midland Naturalist Monograph No. 7 



in the northern half of the state; first col- 

 lected near Oquawka, Henderson Co., by H. 



N. Patterson P. illinoensis Morong 



16. Floating leaves oval, mucronate, 1-3 cm wide; 

 submerged leaves narrowly lanceolate; fruit 

 tipped by the nearly sessile stigma; ponds, 

 ditches, and streams, not uncommon. [P. 



nodosus Poir. (?)] P. anuricanus C. & S. 



15. Mature spikes 1-2 cm long; floating leaves oval, 1-3 

 cm wide; submerged leaves lanceolate, acumi- 

 nate or cuspidate; ponds or slow streams, chief- 

 ly in the eastern part of the state 



- P. ^ramitu'us L. 



12. Submerged leaves linear or filiform, not more than 5 mm 

 wide. 

 17. Submerged leaves linear, 2-5 mm wide, conspicuously 

 reticidate along the midvein; ponds and lakes, not 



common; Fulton, Hancock, and Lake counties 



- P. epihydrus Raf. 



17. Submerged leaves filiform, 1-2 mm wide. 



18. Spikes of 2 kinds: one emersed, cylindrical, many- 

 flowered, the other submerged, globose, few- 

 flowered; ditches and slow streams, not imcom- 

 nion ; chiefly in the w. and s. coimties. [P. hyhridus 



of Michx. and Am. auth.] P. diversifolius Raf. 



18. Spikes all alike, cylindrical. 



19. Blades of the floating leaves less than 1.5 cm long, 

 equalling or longer than the petioles; spikes less 



than 1 cm long; lakes, rare; McHenry Co 



P. vaseyi Robbins 



19. Blades of the floating leaves 2.5 cm or more in 

 length, mostly .shorter than the petioles; spikes 1.5 

 cm or more in length; lakes, ponds, and ditches, 

 not uncommon P. natans L. 



2. Zannichellia L. — Horned Pondweed 



Z palustris L. Ditches and ponds, not common; Fulton, Hender- 

 son, Henry, Menard, Peoria, and Winnebago counties. 



130. Liliaceae Adans. — Lily Family 

 1. Stem leafy (bearing one or more leaves). 



2. Flowers large, 4-10 cm long; leaves alternate or whorled; fruit a capsule 



1 1. Liliuin 



2. Flowers smaller. 

 3. Leaves whorled. 



4. Flowers several; leaves in usually two whorls, parallel-veined 



23. Medeola 



4. Flowers solitary; leaves in one whorl, net-veined 24. Trillium 



3. Leaves alternate. 



