114 American Midland Naturalist Monograph No. 7 



2. Petals yellow, white, or cream, obtuse or retuse; receptacle not 

 becoming enlarged and spongy. 



3. Leaves (except the uppermost in P. arguta) pinnate. 



4. Flowers solitary on small pedicels; petals yellow; plants 

 stoloniferous; leaflets 7-21, with smaller intermediate 

 ones, sharply serrate, whitish silky-pubescent beneath; 

 wet ground, Lake and Cook counties. May-Aug. 



[Argentina anserina (L.) Rydb.]. Silverweed 



P. anserina L. 



4. Flowers cymose; leaflets not whitish pubescent beneath; 



plants not stoloniferous. 



5. Petals white or cream; flowers 12-20 mm in diameter; 



stamens 30; style nearly basal; stem stout, 0.5-1 m tall, 



glandular-pubescent; gravelly soil in the northern 



half of 111., not common. June-July. [Drymocallis 



agrimonioides (Pursh) Rydb.]. Tall C'inquefoil 



P. arguta Pursh 



5. Petals yellow; flowers 6-10 mm in diameter; stamens 20; 

 style terminal ; stem decumbent at base, 20-40 cm tall ; 



wet ground, rare. St. Clair Co., Breiidel 



P. paradoxa Nutt. 



3. Leaves palmate. 



6. Flowers cymose. 



7. Leaflets silvery-pubescent beneath; petals 4-5 mm long; 

 sandy or gravelly soil in the northern half of the state; 



nat. from Eur. May-Sept. Silvery Cinquefoil 



P. argentea L. 



7. Leaflets green on both sides. 



8. Leaflets 5-9; petals pale yellow, about 1 cm long, 

 longer than the sepals; stamens about 30; mature 

 achenes reticulate; waste places and along roads, 

 common; native of Eur. May-July. [P. sulpJiurea 



Lam.] P. recta L. 



8. Leaflets 3 or 5 ; petals yellow, equalling or shorter than 



the sepals. 



9. Leaves 3-foliolate ; plants annual or biennial ; style 



fusifomi, glandular at the base. 



10. Petals obovate; stamens 15-20; achenes striate 



when ripe, about 1 mm long; moist ground, 



common throughout 111, May-Oct. Rough 



Cinquefoil. [P. norvegica L.] 



P. monspeliensis L. 



10. Petals cuneate; stamens about 10; achenes 

 smooth, 0.5-0.7 mm long; moist ground, s.w. 



111., rare. June-July P. millegrana Engelm. 



9. Leaves usually 5-toliolate: j^lants perennial; style 



