232 THE AMERICAN MIDLAND NATURALIST 
ANALYTICAL Kgy.* 
Achenes lenticular; stigmas two. 
Lateral spikes short, sessile; staminate flowers at base or apex of 
spikes, or plants at times with heads dioecious or nearly so. 
Rootstocks long, creeping, the culms 1—few togéther............ I 
Culm cespitose, the rootstocks at most short creeping 
Staminate flowers at top of spikes....... eRe BS wee eh. BALL 
Staminate ‘flowers at bottom of, spikes... .0 7.) ...-2 2. ee III 
Lateral spikes elongated, slender, peduncled, the terminal normally 
BS hatiTaCe is cals ket) Gouci lak oS Shen eceda dat LL Seas cal oe ae ee «IV 
Achenes triangular; stigmas three f 
Perey nia. pubescent .4 0 <)iccs sow vs ottcede psaow ad) Ae Sala eactalde ie Dea ee V 
Perigynia glabrous or tuberculate-hispid:.:'.\.5 0. cola ne to nee VI 
10 
Spikes 10 or less, distinct; sheats hyaline opposite blades. 
Heads not dioecious; styles short; perigynia short-beaked. 
Leaf blades narrowly involute; rootstocks very slender, light 
EO Wa Sole Me le ee ae ee Eee ote 1. C. stenophylla 
Leaf blades 1.5-4 mm. wide, flat above; rootstocks stout, brownish 
|) Ec) “Alaa Sede mA aa Sm eee Marae Le ne Sco eB Fat OU a PAIS 2. C. camporum 
Heads dioecious; styles long; perigynia long-beaked.....3. C. Douglasw 
Spikes very numerous, the upper closely aggregated; sheaths green 
striate, ,oppesitel, blades... 2.0. B41) noe bese eine hee ee 4. C. Sartwella 
II. 
Spikes not very numerous, in a simple head. 
Perigynia deep green at maturity, the spikes all separate..5. C. rosea radiata 
Perigynia yellowish, brownish or reddish at maturity; the upper 
spikes aggregated. 
Perigynia not nerved on inner face and not prominently corky 
thickened at base. 
Perigynia spreading at maturity, reddish tinged, 2.5 mm. wide. 
6. C. gravida 
Perigynia appressed at maturity, not reddish tinged, 1.25 
TTT WAS pO Sis erse SIME Ua gcd 5 Ade) ee a eee 7. C. Hookeriana 
Perigynia strongly nerved on inner face, corky thickened at 
BASE 24 store fia eS Fie inte nace token as ene 8. C. stipata 
Spikes very numerous in a compound head................ g. C. vulpinoidea 
EGE 
Perigynia thin or wing margined. 
Bracts leaf-like, many times exceeding head. 
Perigynia subulate, the beak 2-3 times length of body 
10. C. sychnocephala. 
* Shortly before this paper went to the printer, Mr. K. K. Mackenzie 
revised the species names and wrote this key. 
