FLORA OF THE DISTRICT OF COLUMBIA. 107 



23. Flavae Tuckerm. 



Perigynia yellowish green, the tips spreading or reflexed; spikes short, aggregate. 

 A single species 79. C. oederi. 



24. Hirtae Tuckerm. 



Wet land plants with short-hairy or glabrous perigynia, usually with short stout 

 teeth, these very thin in C. vestita, however. 



Perigynia glabrous 80. C. lacustris. 



Perigynia densely pubescent. 



Beak of perigynium strongly bidentate 81. C. lanuginosa. 



Beak of perigynium not strongly bidentate 82. C. vestita. 



25. Pseudocyperae Tuckerm. 



Perigynia many-nerved, scarcely inflated. Swamp and marsh plants. 



Teeth of the perigynium 1.2-2 mm. long; plants stout 83. C. comosa. 



Teeth of the perigynium less than 1 mm. long; plants somewhat slender. 



84. C. hystericina. 

 26. Physocarpae Drejer. 



Late specks, usually not mature before midsummer; relatively tall. 



Body of the perigynium obconic or obovoid, truncately contracted into a prominent 

 beak. 

 Perigynia shorter than the rough-awned scales; terminal spike small, usually 



etaminate 85. C. frankii. 



Perigynia longer than the scales; terminal spike with both staminate and pistillate 

 flowers. 



Spikes oval; scales acuminate or awned 86. C. squarrosa. 



Spikes oblong-cylindric; scales blunt 87. C. typhina. 



Body of the perigynium lanceolate to ovoid, not truncately contracted. 



Perigynia lanceolate or lance-subulate, tapering into the beak, many-nerved. 



Perigynia yellowish green, the teeth straight 88. C. folliculata. 



Perigynia bright green, the teeth refracted 89. C. collinsii. 



Perigynia broader, abruptly contracted into the beak, usually strongly ribbed. 

 Length of perigynia less than 10 mm. 



Scales rough-cuspidate; staminate spike solitary 90. C. lurida. 



Scales obtuse to short-cuspidate, not roughened; staminate spikes 2 or more. 

 Culms scarcely spongy at the base; leaves scarcely or not at all nodulose; 



beak of perigynium usually roughened 91. C. bullata. 



Culms thick and spongy at the base; leaves strongly nodulose; beak of 



perigynium smooth ■ 92. C. rostrata. 



Length of perigynia 10 mm. or more. Staminate spike solitary. 



Pistillate spikes globose or subglobose; style straight 93. C. intumescens. 



Pistillate spikes oblong or cylindric; style abruptly bent. 

 Culms arising singly from an elongate rootstock; leaves 2-5 mm. wide. 



94. C. louisianica. 

 Culms cespitose; leaves 4-10 mm. wide 95. C. lupulina. 



1. Carex retroflexa MuM. 



Thickets and dry woods; fairly common; chiefly in the Piedmont Region; also at 

 Ammendale. May 10-June 1. Eastern U. S. 



2. Carex convoluta Mackenzie. 



Damp or rich woods; common in the Piedmont Region; also along Paint Branch, 

 and at Ammendale. Mav-June. Me. to Neb. and Ala. (C. rosea of Ward's Flora.) 



