208 CYPERACEAE (SEDGE FAMILY) 



Spikes distinct; the lowest 4-5 mm. thick; the ter- 

 minal 1-1.8 cm. long; perigynia pale, about equaled 

 by the yellowish-brown blunt scales . . . . 38. (7. norvegica. 

 Spikes approximate; the lowest less than 4 mm. thick; 

 plant weak, lax ; leaves involute, 0.5-1.5 mm. broad ; 

 perigynia pale brown or drab. 



Perigynia fusiform 39. C. glareosa. 



Perigynia ovoid (39) C. glareosa, v. amphigena 



A . Staminate flowers borne at the top of the spikes k. 



k. Perigynia ellipsoid-ovoid, scarcely compressed, nearly terete . 40. C. tenella. 

 k. Perigynia compressed I. 



I. Spikes 2 or more in a simple or compound spicate or paniculate 



inflorescence m. 



m. Rootstocks short and thick; culm sin terminal tufts or stools n. 

 n. Spikes green or nearly so when mature (becoming brown 



only when over-ripe) o. 

 o. Broadest leaves 1-4.5 mm. wide p. 

 p. Perigynia very spongy below the middle, the nerve-like 



margins inflexed q. 

 q. Perigynia with minutely serrulate margins ; scales 



blunt ; spikes mostly remote. 

 Perigynia quickly becoming squarrose. 



Culms erect; spikes 6-15-flowered . . .41. C. rosea. 

 Culms loosely spreading ; spikes 2-6-flowered (41) C. rosea, v. radiata. 



Perigynia ascending in fruit (41) C. rosea, v. minor. 



q. Perigynia with smooth margins ; scales acuminate ; 

 spikes mostly approximate. 



Perigynia ovoid ' 42. C. retraftexa. 



Perigynia lance-subulate . . . . (42) C. retraftexa, v. texensis. 

 p. Perigynia of essentially uniform (membranous) texture 

 throughout, not conspicuously spongy below the 

 middle ; margins slightly if at all inflexed /. 



r. Perigynia 4-6 mm. long 43. C. muricata. 



r. Perigynia less than 4 mm. long . 



8. Leaves and culms stiff and wiry; heads 2 (rarely 

 1.5)-4 cm. long. 



Perigynia distinctly nerved 44. a MuJileribergii. 



Perigynia nerveless .... (44) C. Muhlenbergii, v. enervis. 

 8. Leaves and culms soft; heads 0.7-1.5 (rarely 1.8) 



cm. long. 

 Perigynia elliptic-ovate, broadest below the 



middle, narrowest at base . . . . 45. C. cephalophora. 

 Perigynia cordate-deltoid, broadest at the cor- 



date or subcordate base . . . . 46. C. Leavenworthii. 

 o. Leaves 5-10 (the narrowest rarely 4.5) mm. wide t. 



t. Perigynia uniformly firm throughout, the outer face 



nerveless or very faintly nerved u. 

 u. Perigynia wing-margined to the base ; spikes mostly 



distinct in a moniliform inflorescence . . .47. C. sparganoides. 

 u. Perigynia wing-margined only above the middle ; 



spikes approximate in a cylindric or ovoid head. 

 Perigynia broad-ovate to suborbicular, nearly 



equaled by the long-pointed scales. 



Culms 2-5 dm. high ; leaves subbasal . . .50. C. gravida. 

 Culms 6-12 dm. high ; leaves remote . . (50) C. gravida, v. laxifolia. 

 Perigynia lance-ovate, twice as long as the thin 



white scale 48. C. cephaloidea. 



t. Perigynia spongy below the middle, the outer face 



prominently ribbed 55. C. conjuncta. 



n. Spikes yellowish or tawny when mature v. 



V. Perigynia firm and uniform in texture, not spongy nor 

 conspicuously inflated below, the beak shorter than 

 or barely equaling the body w. 

 w. Perigynia straw-color, thin, distinctly flattened on the 



inner face x. 



as. Membranous band of the leaf-sheath not cross-puck- 

 ered ; scales acuminate, rarely awned y. 

 y. Leaves 2^3 mm. wide ; culms firm, without thin 



wing-margins 43. C. muricata. 



y. Leaves 4-S mm. wide ; culms soft, with almost wing- 

 like angles. 

 Beak nearly as long as the narrow-ovate body 



of the perigynium 49. C. alopecoidea. 



Beak one third as long as the broad-ovate or sub- 

 orbicular body of the perigynium. 



Culms 2-5 dm. high ; leaves subbasal . . 50. C. gravida. 

 Culms 6-12 dm. high ; leaves remote (50) C. gravida, v. laxifolia. 



as. Membranous or chartaceous band of the leaf-sheath 

 cross-puckered, at least in age ; scales awn-tipped. 



