FERNALD. — CARICES OF SECTION HYPARRHENAE. 461 



- Bracts wanting or setaceous, if broad at most twice as long as the spike. 

 = Plant strongly stoloniferous ; culms rising from an elongated root- 

 stock : perigynium firm, 5 to (3 mm. long (4) C. siccata. 



= Plant not strongly stoloniferous ; culms solitary or in stools. 

 a. Perigynia less than 2 mm. broad. 



1. Perigynia 5 mm. or more long. 



O Perigynia 7 to 10 mm. long: spikelets oblong-cylindric, pointed, 



1.5 to 2.5 cm. long (1) C. muskingumensis. 



O O Perigynia shorter (or, when exceptionally 7 mm. long, in 

 shorter spikelets). 

 + Perigynia half as broad as long, plump, nerveless or obscurely 



short-nerved on the inner face (21) C.aenea. 



+ + Perigynia one-third as broad as long. 



X Perigynia thin and scale-like, scarcely distended over the 

 achenes, distinctly nerved on the inner face, and promi- 

 nently exceeding the subtending scales. 

 § Leaves at most 3 mm. wide : spikelets 8 to 9, glossy 

 brown or straw-colored, pointed. 

 Spike oblong-ovoid or subcylindric, with ascending 



approximate spikelets (2) C. scoparia. 



Spike moniliform . . (2) C. scoparia, var. moniliformis. 



Spike short-globose or broad-ovoid, the spikelets 

 crowded and divergent . 



(2) C. scoparia, var. condensa. 

 § § Leaves more than 3 mm. wide: spikelets 8 to 14, green 



or dull brown, blunt (3) C. tribuloides. 



(For vars. see below.) 

 X X Perigynia firm, obviously distended over the achenes, 

 nervele s or obscurely nerved on the inner faces, 

 equalled by the subtending scales .... (7) C. praticola. 



2. Perigynia less than 5 mm. long. 



O Perigynia thin and scale-like, scarcely distended over the 

 achenes : leaves 3 to 8 mm. broad. 

 -f Perigynia with appressed tips. 



Spike oblong, the spikelets approximate . (3) C. tribuloides. 

 Spike moniliform, the 6pikelets scattered 



(3) C. tribuloides, var. turbata. 

 + + Perigynia with spreading tips : spike flexuous 



(3) C. tribuloides, var. reducta. 

 O O Perigynia firm, obviously distended over the achenes. 



-f- Perigynia elongate-lanceolate or subulate, less than one-third 

 as broad as long, at most 1.4 mm. broad. 

 X Tips of perigynia conspicuously exceeding the lance- 

 subulate dull scales. 



Culms 1 to 4 dm. high : leaves 1 to 2.5 mm. wide : 

 spikelets 3 to 7 mm. long (5) C. Craw/ordii. 



