Jones: Flora of Illinois, 23. Cyperaceae 85 



Group VII 



Perigynia more or less pubescent or puberulent (sometimes only slightly 

 so); stigmas 3; achenes trigonal. 



1. Perigynium beakless, or the beak less than 0.4 mm. long. 



2. Terminal spike staminate throughout; perigynia 2.5-3 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 n. half of 

 111 C. digitalis Willd. 



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



hyaline-margined glumes; leaves 2-2.5 mm. wide; dry, rocky soil 



C. ricbardsonii R. Br. 



2. Terminal spike with some pistillate flowers. 



4. Perigynia 3.5-4.5 mm. long; dry woods C. pedunculata Muhl. 



4. Perigynia 2-2.5 mm. long. 



5. Stems usually shorter than the leaves; pistillate spikes ellipsoid; 



perigynia obovoid; woods and roadsides, not common 



C. swanii (Fern.) Mack. 



5. Stems usually longer than the leaves; pistillate spikes cylindrical; 



perigynia ellipsoid; woods, n.e. Ill C. virescens Muhl. 



1. Beak of the perigynium 0.4-2 mm. long; terminal spike (or spikes) wholly 

 staminate. 

 6. Mature perigynia 12-18 mm. long; leaves 5-15 mm. wide; moist woods, 



comm^on C. grayii Carey 



6. Perigynia shorter. 



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



C. trichocarpa Muhl. 



7. Perigynia 2.5-5 mm. long. 



8. Some, or all, of 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, chiefly in the n. half of the state 



C. umbellata Schk. 



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



9. Leaves pubescent; woods, common. [C. pubescens sensu Muhl., 

 non Poir.} C. hntijolia Mack. 



9. Leaves glabrous. 



10. Pistillate spikes 3-12 mm. long. 



11. Staminate spike stout, 2-4 mm. thick; body of the perigyn- 

 ium suborbicular, about as long as wide; plants strongly 

 stoloniferous, the stolons slender, reddish, fibrillose, scaly; 



dry open woods, common, flowering in early spring 



C. pennsylvanica Lam. 



1 1 . Staminate .spike 0.5-2 mm. thick; body of the perigynium 

 ellipsoid, longer than wide. 



