Jones: Flora of Illinois, 62. Ranunculaceae 129 



9. Ranunculus L. — Buttercup 



{Datrachium S. F. Gray) 

 1 . Petals white; achenes transversely wtiiikled; plants aquatic. 



2. Beak of achene 0.5-1 mm. long; leaves rigid, not collapsing when wirh- 

 drav/n from the water; ponds and slow streams. May-July. [/?. circi- 

 natiis sensu auth., non Sibth.} R. longirostrts Godr. 



2. Beak of achene minute; leaves soft, usually collapsing when withdrawn 



from the water; ponds and slow streams. May-July. {R. aquatilis L., 

 var. capillaceus DC.} R. trichopbyllus Chaix 



1. Petals yellow; achenes not transversely wrinkled. 



3. Plants stoloniferous, the cordate or reniform crenate glabrous leaves 



basal and at the nodes of the stolons; flowers 6-8 mm. in diameter, the 

 5-8 petals slightly shorter than the oval sepals; achenes thin-v/alled, dis- 

 tinctly striate or ribbed, minutely apiculate, in ellipsoid heads 5-15 mm. 

 long; wet sandy soil, n. 111., not common. May-July. \^Oxygraphis cym- 



balaria (Pursh) Prantl; Halerpestes cymbalaria (Pursh) GreeneJ 



R. cymbalaria Pursh 



3. Plants not stonoliferous; achenes not thin-walled or striate. 



4. Plants aquatic, immersed in water or creeping on mud, the leaves pal- 

 mately lobed or divided, or finely dissected into filiform divisions. 

 June-Aug. [R. delphinifolius Torr.} R. flabellaris Raf. 



4. Plants not floating; if stems creeping in mud and rooting at the nodes, 

 the leaves not finely dissected. 



5. Basal leaves merely denticulate or crenate. 



6. Leaves lanceolate or oblong- lanceolate, remotely denticulate. 



7. Achenes compressed, the body 1-2 mm. long, the beak subulate, 

 1 mm. long; head of achenes 6-8 mm. in diameter; plants 

 perennial; swamps or ditches, local. June-Aug. [R. obtusius- 

 cidus Raf. and R. laxicaulis (T. dC G.) Darby, are nomina 

 dubia.} R. ambigens Wats. 



7. Achenes turgid, keeled, 0.7-1 mm. long, apiculate; head of 



achenes 3-4 mm. in diameter; plants annual; wet ground, s. 



III. May-June R. oblongijolius Ell. 



6. Basal leaves reniform or cordate, merely crenate (some of the 

 later ones often lobed or cleft) ; stem-leaves cleft or lobed; 

 achenes minutely beaked, in globose bear's. 



8. Petals much longer than the sepals; flowers 1.5 cm. or more in 



diameter; plant more or less pubescent; prairies, Jo Daviess 

 Co., May 1891, Pepoon. [R. oralis Raf. (?); R. brevicaulis 



Hook.} Prairie Buttercup R. rhomboideus Goldie 



8. Petals shorter than the sepals; flowers less than 1 cm. in diam- 

 eter; plant glabrous or nearly so; moist ground, very common. 



Apr. -May. Small-flowered Buttercup R. abortivus L. 



5. Leaves all lobed or divided. 



9. Petals not longer than the sepals; flowers less than 1 cm. in diam- 

 eter. 



