118 CYPERACEAE 



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



purplish tinged at base. 



Per igynia flat. 118. C. Tolmiei. 



Perigynia round in cross-section, many-nerved. 119. C. Eaynoldsii. 



Terminal spike gynaecandrous. 



Perigynia 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. 

 Perigynia 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 apex 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 nob papery; peri- 



gynia 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 perigynia. 



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



124. C. atrosquama. 

 Perigynia strongly compressed. 



Perigynia sharp-edged, the margins much narrower than the achene; 



lateral spikes linear. 

 Scales shining, with the midvein conspicuous the whole length, 



exceeded by the perigynia. 125. C. bella. 



Scales dull with inconspicuous midvein, about covering the 



perigynia. 126. C. atratiformis. 



Perigynia widely margined, the margins as wide as the achene; lateral 



spikes oblong or linear-oblong or ovoid. 

 Perigynia granular-roughened; achenes 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 perigynia; 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-cylindric : walls of the perigynia papery; perigynia 5 

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

 gynia. 130. C. Mertensii. 



41. ACUTAE. 

 Culms phyllopodic. 



Beak of the perigynia, if present, not deeply bidentate. 



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

 vein; culms low, stiff, solitary or in small clumps, freely stoloniferous. 

 Perigynia plano-convex, puncticulate, appressed. 131. C. concolor. 



Perigynia 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. 



Perigynia not turgid, appressed or ascending. 



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

 Perigynia substipitate, glaucous, granular-roughened all over, the 



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



Perigynia strongly stipitate, green, granular-roughened at the apex 



only, the body half as wide as long. 136. C. Kelloggii. 



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

 blades 26 mm. wide. 

 Perigynia narrowly to very broadly elliptic, broadest below apex, less 



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



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



wide. 138. C. substricta. 



Beak of the perigynia markedly bidentate, the body strongly ribbed. 



139. C. nebraskensis. 

 Fertile culms aphyllopodic. 



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



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



42. HIRTAE. 



Beak of the perigynia much shorter than the body, the teeth 1 mm. long or less. 

 Perigynia glabrous to sparsely pubescent. 142. C. lacustris. 



