118 CYPERACEAE , 



Culms many-leaved, clothed at base with dried-up leaves of previous year, not 

 purpUsh tinged at base. 

 Perigynia flat. 118. C. Tolmiei. 



Perigj-nia round in cross-section, many-nerved. 119. C. Raynoldsii. 



Terminal spike gj-naecandrous. 



Perigj-nia triangular in cross-section, nerveless or nearly so, 2.5 mm. long or less. 



120. C. Halleri. 

 Perigynia longer, many-nerved or with two prominent marginal nerves, more or 

 less strongly flattened. 

 Spikes contiguous, sessile or short-peduncled, forming a dense head; culms 

 stiff, erect. 

 Perigj-nia subinflated-triangular, scarcely compressed, the beak 1 mm. 



long. 121. C. Nelsonii. 



Perigynia strongly compressed, the beak 0.5 mm. long. 



Lowest spike slightly separate, short-peduncled; scales black, with 

 very conspicuous white hyaline ape.x and upper margins. 



122. C. albo-nigra. 

 Spikes closely contiguous and sessile; scales black with inconspicuous 

 hyaline apex and margins. 123. C. nova. 



Lowest spike (or spikes) strongly peduncled. usually distant, erect or nodding. 

 Spikes 3-5, not oblong-cylindrij; walls of the perigynia not papery: peri- 

 gjTiia 2.5—4.5 mm. long, nerveless or obscurely nerved on the face, 

 dull green to brownish black; scales from a little shorter to a little 

 longer than the perigj-nia. 

 Perigynia slightly inflated and sub-triangular, not strongly compressed. 



124. C. atrosquama. 

 Perigj-nia strongly compressed. 



Perigj-nia sharp-edged, the margins much narrower than the achene; 

 lateral spikes linear. 

 Scales sliining, with the midvein conspicuous the whole length, 



exceeded by the perigyriia. 125. C. bclla. 



Scales dull w-ith inconspicuous midvein, about covering the 

 perigynia. 126. C. atratifonnis. 



Perigyrua widel j' margined, the margins as wide as the achene ; lateral 

 spikes oblong or linear-oblong or ovoid. 

 Perigynia granular-roughened; aclienes short-stipitate. 



Upper pistillate scales exceeding the perigynia; lateral spikes 

 ovoid; lowest peduncle less than the length of the spike. 



127. C. chalciolepis. 

 Upper pistillate scales exceeded by the perigj-nia; lateral 

 spikes oblong or linear-oblong; lowest peduncle 1-2 times 

 as long as the spike. 128. C. atrata. 



Perigynia smooth; achenes strongly stipitate. 



129. C. epapillosa. 

 Spikes 6-10, oblong-cj-lindric: walls of the perigjmia paperj-; perigj-nia 5 

 mm. long, lightly 3-nerved, light green, much shorter than the peri- 

 gynia. 130. C. Mertensii. 



41. ACUTAE. 



Culms phj-llopodic. 



Beak of the perigynia, if present, not deeplj' bidentate. 



Lowest bract exceeded by the inflorescence; scales with obsolete or slender mid- 

 vein; culms low, stiff, solitary or in small chimps, freelj' stoloniferous. 

 Perigj-nia plano-convex, puncticulate, appressed. 131. C. concolor. 



Perigjmia soon turgid, papillose, spreading. 



Scales ovate, exceeded by the perigynia. 132. C. scopulorum. 



Scales lanceolate, exceeding the perigynia. 133. C. chimaphila. 



Lowest bract exceeding the inflorescence; scales usually with a slender midvein or 

 broad light-colored center; culms taller, less stiff, in larger clumps. 

 Perigynia turgid, spreading. 134. C. aperta. 



Perigj-nia not turgid, appressed or ascending. 



Stolons absent; perigynia conspicuouslj- nerved; leaf-blades 1-3 mm. wide. 

 Perigynia substi])itate, glaucous, granular-roughened all over, the 



body two-thirds as wide as long. 135. C. lenticularis. 



Perigj-nia strongly stipitate. green, granular-roughened at the apex 

 onlj-, the body half as wide as long. 136. C. Kelloggii. 



Stolons present, long; perigynia nerveless or inconspicuously nerved; leaf- 

 blades 2-6 mm. wide. 

 Perigj-nia narrowlj to very broadly elliptic, broadest below apex, less 



than 3 mm. long, 1-1.5 mm. wide. 137. C. aquatilis. 



Perigvnia strongly obovate, broadest at the apex, 3 mm. long, 1.75 mm. 

 wide. 138. C. substricla. 



Beak of the perigynia markedly bidentate, the bodj- strongly ribbed. 



139. C. ncbraskensis. 

 Fertile culms aphyllopodic. 



Lower sheaths smooth; scales not blackish. 140. C. Emoryi. 



Lower sheaths strongly hispidulous; scales blackish. 141. C. prionophylla. 



42. HiRTAE. 



Beak of the perigj-nia much shorter than the body, the teeth 1 mm. long or less. 

 Perigj-nia glabrous to sparsely pubescent. 142. C. lacustris. 



