326 



CYPERACEAE. 



VOL. I. 



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



Eriophorum virginicum L. Sp. PI. 53. 1/53. 



. 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, \"-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 

 S-rierved; bristles numerous, dingy brown, rarely white, 

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

 oblong, acute, apicnlate, 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'-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. snbterminalis. 



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. 5". Hallii. 



Achene smooth or very slightly roughened. 8. 5". 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. 



IS. S. occidentalis. 



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



Spikelets several, spicate. 17. S.rufus. 



11. 5". Torreyi. 



12. S. mucronafus. 



13. S. etnberculatiis. 



T 4. S. validus. 



