5. Eleocharis R. Br. Spikerush 



Annual or perennial broomlike sedges usually in aquatic environments; leaves 

 reduced to mere bladeless sheaths; inflorescence solitary, terminal, spiciform (the 

 bract reduced to a mere basal scale or usually absent), bearing few to many 

 perfect flowers crowded in 3 to many ranks; scales spirally imbricate or rarely 

 distichous (as in E. Baldwinii and perhaps E. minima), usually closely crowded, 

 remaining so even when the achenes mature in some species (in others serially 

 deciduous starting at the base of the spike), of various textures but always glabrous; 

 perianth bristles 6 to 9 (or in some species reduced or absent); stamens usually 3, 

 in some species often reduced to 2 or 1; styles 2- or 3-branched, basally enlarged 

 into a persistent base (called the "tubercle") capping the achene, with a post- 

 anthetic zone of abscission between this base and the more slender portion, 

 variously shaped and textured, either well-demarcated from the body of the 

 achene or appearing to merge with it (as in E. parvula and E. obtusa, etc.); achene 

 body plano-convex or isolaterally or isosceleslike trigonous (the trigony often 

 obscure) to nearly terete, of various shapes, textures, colors and surficial sculptur- 

 ing. 



A cosmopolitan genus said to comprise about 200 species. 



1. Tubercle 1.2-1.7 mm. long, about as broad as the body of the achene 



1. E. tuberculosa. 



1. Tubercle less than 1.1 mm. long (2) 



2(1). Achenes with about 6 longitudinal ridges with fine horizontal lines (tra- 

 beculae) between the ridges (3) 



2. Achenes various but not trabeculate (6) 



3(2). Culms strongly compressed, 2-edged, often C-shaped in transection, 0.6-1.3 

 mm. broad 2. E. Wolfii. 



3. Culms neither strongly compressed nor 2-edged (4) 



4(3). Anthers 0.5-1 mm. long 3. E. acicularis. 



4. Anthers less than 0.5 mm. long (5) 



5(4). Anthers 0.3-0.4 mm. long; perennial with creeping rootstocks 



4. E. radicans. 



5. Anthers 0.25-0.4 mm. long; aimual, forming dense tufts 5. E. bella. 



6(2). Culms sharply triquetrous or quadrangular in transection, 2.5-4 mm. broad 

 across each side, 5-8 dm. long (7) 



6. Culms not as above, if triquetrous or quadrangular then much less coarse (8) 



7(6). Culms quadrangular; achenial body 1.7-2.3 mm. long; tubercle 1-1.5 mm. 

 long 6. E. quadrangulata. 



7. Culms triquetrous; achenial body 1.4-1.7 mm. long; tubercle 0.7-1 mm. long 



7. E. fistulosa. 



8(6). Tubercle coronalike, 0.3-0.5 mm. high, 0.8-1 mm. broad, capping and 



often broader than the trigonous obpyramidal body 



8. E. melanocarpa. 



8. Tubercle not as above, if coronalike then the body not trigonous (9) 



9(8). Achene biconvex, lustrous, brown when mature; style branches 2; tubercle 

 forming a narrow lamelliform cap on and in outline confluent with 

 the body (10) 



9. Achene trigonous or biconvex, if biconvex then the style branches 3 and/ or 



the tubercle not lamelliform (11) 



10(9). Spikelcts lanceolate, acuminate; scales acute 9. E. lanceolata. 



10. Spikelets broadly ovoid to ovoid-cylindric, obtuse; scales obtuse.... 10. E. obtusa. 



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