314 American Midland Naturalist Monograph No. 7 



10. Tips of the perigynia appressed or ascending; in- 

 florescence compact, stiff; spikes 7-12 mm long; 

 meadows and ditclies, common. [C. tribuloides 



var. sanganionensis Clokey] 



C. tribuloides Wahl. 



10. Tips of the perigynia spreading; spikes 4-8 mm 



long. 



1 1. Inflorescence compact; spikes globose, echi- 



nate; stems stiff; perigynia 3-4 mm long; 



meadows, roadside ditches, and thickets, 



chiefly in the northern half of the state. 



[C cristata Schw., non Clairv.] 



C. cristatella Britt. 



1 1. Inflorescence loose, flexuous, elongate; stems 

 slender, weak; perigynia 4-5 min long; 

 moist ground, rare; Jackson and Menard 



counties C. projecta Mack. 



7. Perigynia oval or ovate-lanceolate to suborbicular, seldom 

 more than twice as long as wide. 

 12. Perigynium-body oval, finely nerved on the inner sur- 

 face; leaf-sheaths ventrally white-hyaline. 

 13. Perigynia brownish; spikes closely aggregated into 

 a head 1-2.5 cm long, not clavate at the base; 

 marshes and ditches chiefly in the n. half of 111. 



C. bcbbii Olney 



13. Perigynia green; spikes contiguous to widely sep- 

 arate, usually more or less clav^ate at the base; 

 inflorescence at matiu'ity 2.5-5 cm long. 

 14. Leaves 3-4 mm wide; moist ground along roads 

 or in open woods, common. [C. mirabilis 



Dewey, non Host] C. normalis Mack. 



14. Leaves 1.5-2.5 mm wide; open woods 



C. tenera Dewey 



12. Perigynium-body ovate-orbicular, nerved on both sur- 

 faces. 

 15. Perigynia 4-5.5 mm long, spreading-ascending; 

 spikes straw-colored or ferrugineous; leaf-sheaths 

 white-hyaline ventrally; woods and roadsides, not 



infrequent C. festucacea Schk. 



15. Perigynia 3.5-4 mm long, closely appressed; spikes 

 grayish-green turning dull brown; leaf-sheaths 

 green-striate; open woods, local. [C. straminea 



sensu auth., non Willd.] C. albolutescens Schw. 



6. Perigynia 2.5-4 mm wide. 

 16. Perigynia 3-5 mm long. 



17. Leaf-sheaths green-striate nearly to the auricle. 



18. Glumes aristate; spikes 4-8 in a flexuous inflores- 

 cence; perigynia nerved ventrally; Athens, 



