69. 
Cyperus 
(from O'Neill, 1941) 
1. Achene lenticular, flat with an edge facing the 
rachilla; styles bifid; spikelets very flat. 
2. Spikelets 1.5 to 2 mm. long, 1-flowered, congested 
into a solitary cluster of dense, sessile heads. 
Expected (C. tenuifolius). 
2. Spikelets 3 to 20 mm. long, 3- to 40- flowered, 
digitate in an umbel-like panicle. 
3. Achene suborbicular, black, transversely 
wrinkled. (Also, spikelets yellow, 2-2.5 mm. 
wide.) Expected (C. flavescens). 
3. Achene obovate to oblong-obovate, purplish- 
brown, not wrinkled. 
4, Spikelets 1 to 1.5 mm. wide. Expected 
(C. polystachyos var. texensis). 
4. Spikelets 2 to 3.5 mm. wide. 
5. Rachilla winged, the wings forming a 
collar .2 to .3 mm. wide at the base 
of the achene; salt marsh habitat......... C. filicinus 
5. Rachilla wingless; freshwater marsh 
habitat. Expected (C. rivularis). 
1. Achene 3-angled; styles trifid; spikelets thicker 
in the center. 
6. Rachilla readily disarticulating into 1-fruited 
joints. Expected (C. odoratus). 
6. Rachilla not articulated or articulating only 
at the base. 
7. Rachilla wingless; stamens 1 or 2 (3 in 
(CG. f£ilicinus). 
8. Glumes long-awned, conspicuously 9- to 
13-nerved; plants scented. Expected 
(C. inflexus). 
8. Glumes obtuse to mucronate, 3-nerved; 
plants odorless. 
