48 CYPERACEAE 



Scales dull with inconspicuous niidvein, 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 a.s the spike. 128. C. atrata. 



PerigjTiia smooth; achenes strongly stipitate. 



129. C. epapillosa. 

 Spikes 6-10, oblong-cylindric: walls of the perigj-nia papery; perigjiiia o 

 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. 

 Perigjniia 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 perigjTiia'. 133. C. chimaphilri. 



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

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

 Perigynia turgid, spreading. 134. C. aperta. 



Perig>Tiia not turgid, appressed or ascending. 



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

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



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



Perig\Tiia strongly stipitate, green, granular-roughened at the apex 

 oiily, 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. aqnalilis. 



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

 wide. 138. C. subslricla. 



Beak of the perigjTiia markedly bidentate, the body stronglj' ribbed. 



139. C. nebraskensis. 

 Fertile culms aphjilopodic. 



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



Lower sheaths stronglj' hispidulous; scales blackish. 141. C. prionophylla. 



42. HlRT.\E. 



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

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



Perigynia densely or stronglj' pubescent. 



Nerves of the perigj-nia obscured by pubescence, the teeth of beak short. 

 Leaf-blades flat, more than 2 mm. wide. 143. C. lanuginosa. 



Leaf-blades involute, 2 mm. wide or less. 144. C. lasiocarpa. 



Nerves of the perigj'nia prominent, the teeth of beak prominent, slender. 



145. C. Houghtonii. 

 Beak of the perigynia including teeth nearly as long as body, the teeth 1.5 mm. long or 

 more. 

 Perig-\-nia glabrous. 



Perigynia ovoid, the teeth less than 2 mm. long, erect or spreading; scales acute 



to aristate; leaf-blades glabrous. 146. C. laeviconica. 



Perigynia lanceolate or ovoid-lanceolate, the teeth 2-4 mm. long, widely spread- 

 ing; scales long-aristate; leaf-blades pubescent beneath. 



147. C. atherodes 

 Perigj-nia hairy. 148. C. Sheldonii. 



43. EXTEN-s.\E. 

 PerigjTiia 2-3 mm. long, the beak scarcely half as long as the body. 149. C. viridula. 

 PerigjTiia 4-6 mm. long,' the beak about as long as the bodj-. 150. C. flava. 



44. P.\UCIFLOR.\E. 



Rhacheola present, conspicuouslj- exserted; culms with many leaves. 



151. C. microglocbin. 

 Rhacheola absent or rudimentarj', not conspicuously exserted; culms with few leaves. 



152. C. pauciflora. 

 45. P.seudo-Cypere.\e. 



Perigj-nia suborbicular in cross-section, more or less inflated. 153. C. hystricina. 

 Perigynia obtusely triangular, scarcely inflated, closely enveloping achene. 



154. C. comosa. 

 46. Physocarp.\e. 



I'erigjnia scarcely inflated; beak entire or emarginate; stigmas normally two and achenes 

 lenticular. 

 PerigjTiia lanceolate; fertile culms fllamentose at the base; rootstocks creeping. 



155. C. miliaris. 



