322 American Midland Naturalist Monograph No. 7 



22. Lower perigynia reflexed or widely spreading; stems 

 scattered, obtusely angled; plants stoloniferous; 

 leaves 4-12 mm wide; ditches and shores, rare; 



Henderson and Winnebago counties 



C. rostrata Stokes 



22. Perigynia ascending; stems cespitose, sharply an- 

 gled; leaves 3-5 mm wide; swamps, and wet 

 ground in woods, local C. vesicaria L. 



group vti 



Perigynia more or less pubescent or puberulent (sometimes only 

 slightly so) ; stigmas 3; achenes trigonal. 



1. Perigynia beakless (or the beak less than 0.4 mm long). 



2. Terminal spike staminate throughout; perigynia 2-3 mm long. 

 3. Perigynia ellipsoid, 3-12 in a spike, longer than, or equalling 

 the glumes; leaves 2.5-5 mm wide; woods and thickets in 

 the northern half of III C. digitalis Willd. 



3. Perigynia obovoid, 10-25 in a spike, shorter than the obtuse, 



hyaline-margined glumes; leaves 2-2.5 mm wide; sandy or 

 rocky barrens, rare; Hancock, Lake, Menard, Peoria, and 



Winnebago counties C. richardsonii R.Br. 



2. Terminal spike with some pistillate flowers. 



4. Perigynia about 4 mm long, puberulent to glabrate, obovoid, 



angular; leaves persistent, 2-5 mm wide, usually longer 



than the slender stems; dry woods, n. 111., rare 



- C. pcdiaiculata Muhl. 



4. Perigynia 2-2.5 mm long. 



5. Stems usually shorter than the leaves; pistillate spikes ellip- 

 soid; perigynia obovoid; woods and roadsides, not 



common C. sivanii (Fern.) Mack. 



5. Stems usually longer than the leaves; pistillate spikes cylin- 

 drical; perigynia ellipsoid; woods, n.e. Ill 



C. virescens Muhl. 



l.Perigynium beaked; terminal spike (or spikes) wholly staminate. 

 6. Mature perigynia 12-18 mm long; leaxes 5-15 mm wide; moist 



woods, common C. grayii Carey 



6. Perigynia shorter. 



7. Perigynia 9-10 mm long; leaves 3-8 mm wide; wet meadows 



in the n. half of 111 C. trichocarpa Muhl. 



7. Perigynia 2.5-5 mm long. 



8. Some (or all) the spikes half hidden among the tufted leaf- 

 bases; plants densely tufted, 5-15 cm tall; pistillate spikes 

 5-10 mm long; perigynia plump, stipitate, 2-keeled, 2.5- 



3.5 mm long; dry sandy or gravelly soil, local 



- C. umbellata Schk. 



8. All the spikes near the summit of the stem. 



