326 



CYPERACEAE. 



VOL. I. 



10. Eriophorum virginicum L. Virginia Cotton-grass. Moss Crop. Fig. 800. 



Eriophorum virginicum L. Sp. PI. 53. 1753. 



E. virginicum album A. Gray, Man. Ed. 5, 566. 1867. 



Culm stiff, rather slender, obtusely triangular above, 

 terete below, smooth, ii-4 tall, rather leafy. Leaves 

 narrowly linear, flat, i"-2|" wide, rough-margined, 

 somewhat channeled toward the apex, the upper often 

 overtopping the culm, those of the involucre 2-4, 

 spreading or deflected, 2'-6' long, i or 2 of them 

 much longer than the spikelets ; spikelets several or 

 numerous in a dense terminal capitate cluster usually 

 broader than high, erect or the outer ones spreading ; 

 scales ovate, acute, brown with a green center, about 

 5-nerved ; bristles numerous, dingy brown, rarely white, 

 about 3 times as long as the scale ; achene linear- 

 oblong, acute, apiculate, light brown. 



In bogs, Newfoundland to Manitoba, south to Florida 

 and Nebraska. June-Sept. 



7. SCIRPUS L. Sp. PI. 47- 1753- 



Annual or perennial very small or very large sedges, with leafy culms or the leaves re- 

 duced to basal sheaths. Spikelets terete or somewhat flattened, solitary, capitate, spicate or 

 umbellate, subtended by a i-several-leaved involucre or the involucre wanting in some 

 species. Scales spirally imbricated all around, usually all fertile, the i or 2 lower sometimes 

 empty. Flowers perfect. Perianth of 1-6, ^slender or rigid, short or elongated, barbed, 

 pubescent or smooth bristles, or none in some species. Stamens 2 or 3. Style 2-3-cleft, not 

 swollen at the base, wholly deciduous from the achene, or its base persistent as a subulate 

 tip. Achene triangular, lenticular or plano-convex. [Latin name of the Bulrush, said to 

 be from sirs, the Celtic word for rushes.] 



About 150 species of wide geographic distribution. Besides the following, some 10 others occur 

 in the southern and western United States. Type species : Scirpus lacustris L. 



1. Spikelet solitary, terminal, bractless or subtended by a single bract or short leaf. 



No involucral bract. 



Culms i '-2' high ; achene smooth ; plant of saline soil. i. S. nanus. 



Culms 3 r -io' high; achene reticulated; plant of fresh-water marshes. 2. S.pauciflorus. 

 Involucral bract present, erect. 



Bract shorter than or but little exceeding the spikelet ; plants not aquatic. 



Culm terete ; leaf of upper sheath subulate ; bristles smooth. 3. S. caespitosus. 



Culms triangular ; leaf of upper sheath linear ; bristles upwardly barbed. 



Leaves shorter than the culm ; scales acute. 4. S. Clintoni. 



Leaves about as long as culm; scales cuspidate or awned. 5. S.planifolius. 



Bract at least twice as long as the spikelet ; plant aquatic. 6. S. subterminalis. 



2. Spikelets normally more than i, usually several or numerous, often appearing lateral; involucral 



bract only i. 

 Spikelets few, 1-12, appearing lateral. 



Culms not sharply 3-angled ; achene plano-convex ; annuals. 



Achene strongly transversely rugose. 7. S. Hallii. 



Achene smooth or very slightly roughened. 8. S. debilis. 



Culms sharply 3-angled ; plants perennial by rootstocks. 



Achene plano-convex ; bristles shorter than or equalling the achene. 



Spikelets acute, much overtopped by the slender involucral leaf ; scales awned. 



9. S. americanus. 

 Spikelets obtuse ; involucral leaf short, stout ; scales mucronulate. 



10. S. Olneyi. 

 Achene 3-angled, ridged on the back. 



Bristles longer than the achene : involucral leaf erect. 

 Bristles as long as the achene ; involucral leaf abruptly bent. 

 Spikelets several or numerous, umbelled ; tall sedges. 

 Culm sharply triangular, equalled by the long leaves. 

 Culm terete ; leaves reduced to sheaths. 

 Styles 2-cleft ; achene lenticular. 



Achenes i" long, nearly as long as the scales; spikelets ovoid. 



Achenes about i l / 2 " long, distinctly shorter than the scales; spikelets oblong-cylindric. 



15. S. occidentalis. 



Style 3-cleft ; achene trigonous. 16. S.heterochaetus. 



Spikelets several, spicate. 17. S.rufus. 



U.S. Torreyi. 



12. S.mucronatus. 



13. S. etuberculatus. 



1 4. S. validus. 



