192 



Cyperaceae 



Scirpus 



50 



Map 363 



Eriophorum virginicum L. 



468. SCIRPUS [Tourn.] L. Bulrush 



[Sr. M. St. Leona Thornton. The Indiana species of Scirpus. Amer. 

 Midland Nat. 15: 292-322. 1934.] 



Sister Thornton's treatment of Indiana Scirpus seems to be compre- 

 hensive and authentic. I have seen most of the specimens she cites. I am 

 accepting her determinations of the few I have not seen and they also are 

 indicated on the distribution maps. 



Involucral bract none. (This is Sr. Thornton's Scirpus pancifloirus which is now re- 

 ferred to Eleocharis pauciflora var. Fernaldii Svenson. (See Rhodora 36: 380. 

 1934.) 

 Involucral bract solitary (the inflorescence appearing as if on the side of the stem). 

 Spikelets 1, 6-13 mm long; stem cylindric, conspicuously nodulose, normally growing 

 in shallow water but often emersed in dry weather; achenes trigonous, about 

 2.5 mm long and about 1.6 mm wide, brown, smooth; bristles retrorsely barbed, 



about equaling the achene 1. S. subterminalis. 



Spikelets normally more than 1. 



Plants usually less than 5 dm high; annuals with tufted roots; culms terete or 



obtusely angled. 



Culms obtusely triangular; mature involucral bract usually divaricate; achenes 



obovoid, unequally biconvex, about 1.7 mm long, surface black with shallow 



and irregular pits; bristles longer than the achene, with increasing width 



toward the base, mostly 0.015 mm wide near the base 2. »S. debilis. 



Culms terete; mature involucral bract usually erect; achenes obovoid, plano- 

 convex, 1.5-1.8 mm long, surface black without pits or with very incon- 

 spicuous ones; bristles very slender, of almost equal width, generally about 

 0.01 mm wide near the base. 



Bristles lacking 3. S. SynitJiii. 



Bristles present, usually 6, sometimes fewer, longer than the achene 



3a. S. Smithii var. setosus. 



Plants usually more than 5 dm high; perennials with creeping rootstocks; culms 

 triangular or terete. 

 Involucral bract much longer than the inflorescence. 



Culms sharply triangular; involucral bract acute; achenes plano-convex, 

 smooth; bristles shorter than the achene 4. S. americanus. 



