3. Ranhnculaceae 55 



16. Leaf-divisions cleft or incised; heads of 

 aciienes ellipsoid, the achenes with 

 short, nearly strait^ht beaks; wet 



ground, not common. July-Aug 



R. pennsylv aniens L.f. 



!3. Petals longer than the sepals; flowers 1..5-2.5 cm in 

 diameter. 

 17. Beak of the mature achene less than 1 mm long, 

 recurved. 

 18. Stem more or less cormose-thickened at base; 

 leaves with the temiinal division stalked; 

 sepals reflexed; fields and roadsides, occa- 

 sional; nat. from Eur.; May-July. Bulbous 



Buttercup R. hulbosus L. 



18. Stem not swollen at base. 



19. Sepals reflexed; achenes usually low 

 tuberculate; terminal leaflet often peti- 

 olulate; pastures, wet fields, and road- 

 sides; adv. from Eur.; s. 111. May 



R. sardous Crantz 



19. Sepals spreading; achenes smooth; ter- 

 minal leaflet sessile; roadsides and 

 fields; nat. from Eur. May-July. Tall 



Buttercup R. acris L. 



17. Beak of the mature achene 1 mm or more in 

 length. 

 20. Petals broadly obovate; plants stoloniferous. 

 21. Beak of the achene cui'ved; mature 

 achene 2-2.5 mm in diameter; road- 

 sides and fields, common ; adv. from 

 Eur. Apr.-Jime. Creeping Buttercup 

 R. re pens L. 



21. Beak nearly straight; mature achene .3-4 



mm in diameter; wet woods, common. 



Apr. -June. Marsh Buttercup 



R. scptcntrionaUs Poir. 



20. Petals oval, oblong, or narrowly obovate; 

 achenes 2-2.5 mm in diameter; plants not 

 stoloniferous. 



22. Stem strigose; leaf-lobes narrow; some ot 



the roots tuberous-thickened; woods 

 and meadows. Apr.-May. Tufted But- 



tercup [R. illinoensis Greene] 



R. fascicularis Muhl. 



22. Stem villous; leaf-lobes oval to oblanceo- 

 late; roots scarcely thickened; woods or 

 roadsides; chiefly in s. 111., but extend- 

 ing northward to Hancock, McLean, 



