462 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Culms taller: leaves broarler : spikelets 8 to 11 mm. long 



(5) C. Crawfordii, var. vigens. 

 X X Tips of perigynia equalled by the ovate bluntish glossy 



dark scales (6) C. oronensis. 



+ + Perigynia broader, nearly or quite half as broad as long. 



X Tips of perigynia distinctly exceeding the subtending 

 scales. 

 § Leaves 2.5 mm. or more wide. 

 □ Spikelets compactly flowered, the mature perigynia 

 with recurved or spreading tips concealing the 



scales (8) C. cristata, 



□ □ Spikelets with ascending or slightly spreading peri- 

 gynia ; scales apparent. 

 A Mature perigynia greenish or pale straw-colored, in 

 loose spikelets : spikes more than 2.2 cm. long 

 (if shorter, with dark chestnut scales). 

 Spikelets approximate in ovoid or oblong spikes. 

 Scales pale, not strongly contrasting with the 



perigynia (10) C. inirabilis. 



Scales dark chestnut, strongly contrasting with 

 the perigynia . . (10) C. mimbilis, var. tincta. 

 Spikelets scattered in a moniliform spike 



(10) C. mirabUis, var. perJonga. 

 A A Mature perigynia brown, in dense spikelets : spikes 

 at most 2.2 cm. long : scales pale brown 



(17) C. Bebbii. 



§ § Leaves narrower. 



Spike stiff, with crowded closely flowered spikelets 



(17) C. Bebbii. 

 Spike flexuous and moniliform, or at least with the 

 loosely flowered spikelets scattered . (11) C. straminea. 

 X X Tips of perigynia equalled by the subtending scales. 



§ Spike stiff and erect, or at least with the spikelets ap- 

 proximate. 

 Spike brown or ferrugineous .... (19) C. leporina. 



Spike brownish white (20) C. xemntica. 



§ § Spike flexuous, or at least with the lower spikelets 

 remote. 

 □ Perigynia nerveless or minutely short-nerved on the 

 inner face. 



Mature perigynia straw-colored or pale brown, one- 

 third as broad as long (7) C praticola. 



Mature perigynia olive-green or bronze, one-half as 



broad as long (21) C. aenea. 



n n Perigynia with strong ribs the length of the inner face : 



spike silvery green (18) C.foenea. 



b. Perigynia 2 mm. or more broad. 

 1. Tips of the perigynia distinctly exceeding the subtending scales. 



