156 American Midland Naturalist Monograph No. 2 



5. Pedicels and leaves pubescent; blades obovate, irregularly serrate; 



pastures and open woods, throughout 111. May-June 



C. punctata Jacq. 



2. Blades prevailingly widest near the middle. 



6. Blades more or less pubescent beneath, at least in the axils of the veins; 

 pedicels pubescent; calyx-lobes usually glandukr-serrulate. 

 7. Lower surface of mature leaves sparsely pubescent along the sides of 

 the veins with short, somewhat stiff hairs; corymbs sparingly 

 pubescent; stamens mostly 10, the filaments short; thorns usually 

 numerous, stout, 5-9 cm. long; banks of streams, chiefly in the n. 

 half of 111. May. [C. corporea Sarg.; C. divida Sarg.; C. ensifera 

 Sarg.; C. gaultii Sarg.; C. laxiflora Sarg.; C. longispina Sarg.; C. 

 rutila Sarg.; C. vegeta Sarg.; C. illinoiensis Ashe; C. rieoflurialis 

 Ashe; C. occidentalis Britt.; C. macracantha of auth., not Loud.] 

 C. succulenta Schrad. 



7. Lower surface of leaves softly pubescent, especially on the veins; 



petioles wing-margined; corymbs tomentose; stamens mostly 20, 

 the filaments slender; thorns few, slender, or none; thickets and 

 open woods, generally distributed in 111., flowering in the latter 

 part of May and early part of June. [C. structilis Ashe; C. tomen- 

 tosa sensu DuRoi, non L.} C. calpodendron (Ehrh.) Medic. 



6. Blades glabrous or essentially so; pedicels glabrous; calyx-lobes entire 

 or nearly so. 



8. Leaves oval or rhombic, acute or acutish, serrate, the base cuneate; 



lower surface with tufts of tomentum in the axils ol the veins; 

 fruit 5-8 mm. in diameter; alluvial soil, w. and s. 111. [C. nitida 

 sensu Egglest., ex p., non Sarg.; C. ovata Sarg.; C. acutifolia 

 Sarg.] C. viridis L. 



8. Leaves short-obovate to suborbicular, usually incised with shallow 

 lobes, these crenate; styles and nutlets usually 2; fruit 1-1.5 cm. 

 in diameter; thickets and open woods, not uncommon. May-June. 

 £C. brownii Britt.] C margaretta Ashe 



1. Leaves prevailingly widest below the middle or toward the subcordate, trun- 

 cate, rounded, or broadly cuneate base. 

 9. Leaves glabrous or nearly so at maturity, or only slightly pubescent be- 

 neath. 



10. Leaves deltoid-cordate (often conspicuously 3-5-Iobed); calyx-lobes 

 deltoid, entire; fruit 5-7 mm. in diameter, the calyx deciduous; 

 chiefly s. III., but extending northw. to Peoria Co. [C. cordata Ait.] 

 C. phaenopyrum (L. f.) Medic. 



10. Leaves otherwise; calyx-lobes lanceolate; fruiting calyx usually persis- 

 tent. 



11. Calyx-lobes entire or nearly so; inflorescence glabrous. 



12. Leaves thin, scabrellous on the upper surface when young, soon 

 glabrous; stamens 10 or fewer; fruiting calyx sessile; thickets, 



