204 



CYPERACEAE 



XV. GRACILLIMAE. 



Perigynia 2-4 mm. long, slightly swollen : spikes linear or linear-cylindric. 



Plants glabrous : perigynia obtuse. 41. C. gracillima. 



Plants with pubescent sheaths : perigynia pointed at both ends. 



Perigynia 2 mm. long : spikes erect or somewhat spreading. 42. (7. aestivalis. 



Perigynia 4 mm. long : spikes drooping, at least when mature. 43. C. oxylepis. 



Perigynia 4-5 mm. long, manifestly swollen : spikes oblong or oblong- 



cylindric. 44. C. Davisii. 



XVI. FLEXILES. 



A single species in our range. 45. C. Cher okeen sis. 



XVII. DEBILES. 



Perigynia membranous, few-nerved : pistillate spikes slender. 



Leaf-blades 1-3 mm. wide : scales as long as the perigynia or nearly so. 46. C. juncea. 

 Leaf-blades 3-8 mm. wide : scales about ^ as long as the perigynia. 

 Perigynia glabrous, or merely puberulent, beaked. 



Perigynia 6 mm. long, the beak short. 47. C. tennis. 



Perigynia 8-10 mm. long, the beak subulate. 48. C. debilis. 



Perigynia pubescent, pointed, scarcely beaked. 49. C. venusta. 



Perigynia leathery, strongly many-nerved : spikes stouter. 50. C. oblita. 



XVIII. GRISEAE. 

 Leaves slightly or not at all glaucous. 



Perigynia little longer or shorter than the scales. 



Pistillate spikes dense, usually many-flowered : leaf-blades 4-6 mm. 



wide, soft, spreading. 51. (7. grisea. 



Pistillate spikes loosely several-flowered : leaf-blades 2-4 mm. wide, 



mostly erect, rigid. 52. C. amphibola. 



Perigynia twice or thrice longer than the scales. 53. C. flaccosperma. 



Leaves, or the whole plant, very glaucous. 54. C. glaucodea. 



XIX. GRANULARES. 



Bracts elongated, mostly overtopping the spikes : perigynia strongly many- 

 nerved. 55. C. granularis. 

 Bracts short, rarely overtopping the spikes : perigynia finely few-nerved. 



Leaf-blades 4-5 mm. wide : pistillate spikes long-ped uncled. 56. C. microdonta. 



Leaf-blades 2-4 mm. wide : pistillate spikes short-peduncled. 57. C. Crawei. 



XX. OLIGOCARPAE. 



Perigynia narrowed at both ends, beakless. 

 Perigynia with short entire beaks. 



XXI. LAXIFLORAE. 



Plants not at all glaucous, or very slightly so. 

 Beak of the perigynium slender, straight. 

 Beak of the perigynium bent, short or wanting. 

 Leaf-blades mostly narrow, 2-12 mm. wide. 

 Scales, at least the upper ones, obtuse. 



Bracts elongated : spikes loosely flowered : stems and scapes 



slender. 



Bracts short : spikes densely flowered : stems and scapes stout. 

 Scales acute, cuspidate, acuminate or awned. 

 Perigynia obtusely 3-angled. 



Perigynia obovoid, 2.5-3 mm. long, the beak short, blunt, bent. 

 Perigynia elliptic to oblong, 3-5 mm. long, the beak sharp. 

 Perigynia narrowly oblong, 4-5 mm. long, the beak oblique. 

 Perigynia elliptic, 3-4 mm. long, the beak nearly straight. 

 Perigynia sharply 3-angled. 



Spikes drooping or spreading : leaf-blades 2-4 mm. wide : peri- 

 gynia about as broad as long. 



Spikes erect or nearly so : leaf -blades 4-12 mm. wide : peri- 

 gynia about twice as long as broad. 

 Leaf-blades 12-36 mm. broad. 

 Plants distinctly glaucous. 



Pistillate spikes drooping from hair-like peduncles. 

 Pistillate spikes erect. 



XXII. DIGITATAE. 

 A single species in our range. 



XXIII. MONTANAE. 

 Plants not stoloniferous. 



Plants stoloniferous, the stolons sometimes short. 

 Scapes, or some of them, longer than the leaves. 



Plant dark green : staminate spike very prominent : perigynia broadly 



oval. 



Plant light green : staminate spike shorter : perigynia oblong. 

 Scapes, or most of them, much shorter than the leaves. 



Scales light green, with purple margins, or these never pale : perigynia 



oblong. 



Scales green, or sparingly dark-blotched. 

 Scales black or with broad black-purple margins. 

 Scales green with lighter scarious margins : perigynia oval. 



58. C. conoidea. 



59. C. oligocarpa. 



60. C. polymorpha. 



61. C. tetanica. 



62. <7. Meadii. 



63. C. laxiflora. 



64. C. styloflexa. 



65. C. striatula. 



66. C. digitalis. 



67. C. Austro-Caroliniana. 



68. C. plantaginea. 



69. C. laxiculmis. 



70. C. ptychocarpa. 



71. C. Baltzdlii. 



72. C. pedicellata. 



73. C. Pennsylvanica. 



74. C. varia. 



75. C. Floridana. 



76. C. nigro-marginata. 



