The Flora of the Cayuga Lake Basin 97 



d. Achenes 1 mm. long; plants low, annual; culms filiform, 1-5 cm. high. 



1. S. nanus 

 d. Achenes 2-2.5 mm. long ; plants taller, perennial, with slender rootstocks ; 

 culms 0.5-1.5 mm. thick, 5-30 cm. high. 2. S. pauciflorus 



c. Bristles upwardly setulose ; spikelets terete ; achenes beakless ; scales with firm 

 green midribs, apiculate. 3. S. planifolius 



b. Perianth bristles in fruit much exceeding the scales (2-3 cm. long), not barbed, 

 flattened. 4. S. hudsonianus 



Involucre consisting of a firm green erect bract, appearing to be a continuation of 



the culm; culms not leafy (see also 3d a), 

 b. Spikelets solitary or in a sessile cluster. 

 c. Culms low, subterete, spreading ; bristles usually wanting. 5. S. Smithii 

 c. Culms taller and more erect, sharply 3-angled; bristles present. 



6. S. americanus 

 b. Spikelets umbellate or panicled. 

 c. Achenes 2 mm. long; scales 2-2.5 mm. long, subglabrous, scarcely spotted, mid- 

 rib conspicuous and greenish ; inflorescence lax ; spikelets ovoid to subcylin- 

 drical ; culms usually soft. 7. S. validus 



c. Achenes 2.5 mm. long; scales 3^1 mm. long, more or less viscid-puberulent on 

 back and much spotted, midrib less evident and more concolorous ; inflores- 

 cence usually condensed ; spikelets clustered, generally cylindrical ; culms 

 usually firm and hard. 8. S. acutus 



Involucre consisting of 2-many leafy bracts ; spikelets capitate or in a compound 



umbel ; culms leafy. 

 b. Spikelets large, 10-50 mm. long, 5-10 mm. wide ; culms sharply 3-angled, springing 

 from strong, often tuberous, creeping rootstocks. 

 c. Achenes sharply and equally 3-angled ; plants stout, 1-2.5 m. high ; leaves 



0.7-2 cm. wide. 9. S. fluviatilis 



c. Achenes lenticular or obscurely and bluntly 3-angled; plants 0.3-1 m. high; 

 leaves stiff, 3-9 mm. wide. 10. 6". campestris, 



var. paludosus 

 b. Spikelets small, 2-15 mm. long, 1-3 mm. wide, more numerous; culms obtusely 

 3-angled or terete. 

 c. Bristles retrorsely barbed ; culms solitary or loosely clustered ; plant with thick 

 scaly stolons ; spikelets in glomerules. 

 d. Lower sheaths red-banded; bristles barbed nearly to the base. 



11. S. rubrotinctin 

 d. Lower sheaths green ; bristles barbed only above the middle. 



e. Bristles scarcely longer than the achene, usually shorter ; spikelets dark 

 brown or dark lead-color. 

 /. Blades 10-18 mm. wide ; lower sheaths cellular-nodulose ; bristles about 



equaling the achene. 12. S. atrovircns 



f. Blades 4-10 mm. wide ; lower sheaths not nodulose ; bristles shorter than 

 or as long as the achene, sometimes wanting; plant more slender. 



12a. S. atrovirens, 

 var. georgianus 

 e. Bristles twice the length of the achene; spikelets rufous-brown. 



13. S. polyphyllus 

 c. Bristles smooth or sparingly upwardly setulose, curly ; plant densely or 

 loosely cespitose, not stoloniferous ; spikelets in glomerules or separate. 

 d. Bristles not exceeding the scales ; spikelets separate, elliptic-oblong, 5-10 



mm. long. 14. S. lineatus 



d. Bristles much exserted at maturity; spikelets 3-9 mm. long. 



e. Fruit late (shedding achenes Aug. (10) 15-Oct. 17) ; spikelets subglobose 

 to elliptic-oval or oblong, all sessile and glomerulate or some pedicelled. 



