3. Ranunculaceae 53 



2. Beak of achene 0.5-1 mm long; leaves rigid, sessile or nearly 

 so, usually 1-1.5 cm long, not collapsing when withdrawn 

 from the water; ponds and slow streams, not common. May- 

 July. [R. circinatus sensu auth., non Sibth.] 



R. longirostris Godr. 



2. Beak of achene minute; leaves soft, mostly petioled, 2-2.5 cm 



long, usually collapsing when withdrawn from the water; 

 ponds and slow streams; absent from the s. counties. May- 

 July. [R. aquatilis L. \ar. capillaceus DC] 



- R. trichophyllus Chaix 



1. Petals yellow; achenes not trans\ersely wrinkled. 



3. Achenes thin-walled, distinctly striate or ribbed, minutely 



apiculate, in ellipsoid heads 5-15 mm long; plants stolonifer- 

 ous, the cordate or renifonii 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; wet sandy 

 soil, not common; Cook, Du Page, Henry, Kane, and Mc- 

 Henry counties. May- July R. cymbalaria Pinsh 



3. Achenes not thin-walled or striate. 



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

 leaves palmately lobed or divided, or finely dissected. 



5. Submersed leaves divided into linear-filiform segments; 

 petals 7-15 mm long; ponds and ditches. Apr.-Jime 

 [R. di'lphinijolius Torr.] R. jlahellaris Raf. 



5. Submersed lea\es orbicidar with 3-5 lobes; petals 4-7 mm 



long; ponds, rare; Cook Co., Munroe in 1877 



R. purshii Richards. 



4. Plants not floating; if stems creeping in mud and rooting 

 at the nodes, the leaves not finely dissected. 



6. Basal leaves merely denticulate or crenate (rarely lobed). 

 7. Leaves lanceolate or linear, or the basal ovate. 



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

 achenes 2-4 mm in diameter; annuals with linear 

 or linear-lanceolate stem-leaves. 

 9. Petals 1-3, pale yellowish, not more than 1-1.5 mm 

 long; stamens 3-10; wet ground, s. 111., not com- 

 mon, extending northward to Macoupin Co. 

 May-June. [R. oblongifolius Ell.]...i?. pusillus Poir. 



9. Petals 5-7, bright yellow, 3-7 mm long; stamens 

 20-25; wet ground, chiefly in s. 111., but extend- 

 ing northward to Fulton Co. May-June. [R. 



texensis Engelm.] 



R. laxicaulis (Torr. & Gray) Darby 



8. Achenes compressed, the body 2 mm long, the subu- 

 late beak 1 mm long; head of achenes 5-8 mm in 

 diameter; petals 5-7 mm long; stamens 30-50; 



