198 



(JYPERACEAE 



lueochans 



Miles 



50 



Map 380 

 Eleocharfs equfsetoides (EIIJ Torr. 



50 



Map 381 

 Eleocharis qaudrangulata 

 (Michy) R. 8, S. var crassior Fern. 



469. ELEOCHARIS K. Br. Spikerush 



[Fernald and Brackett. The representatives of Eleocharis palustris in 

 North America. Rhodora 31 : 56-77. 1929. Svenson. Monographic studies 

 in the genus Eleocharis. Rhodora 31 : 121-135, 152-163, 167-191, 199-219, 

 224-242. 1929; 34: 193-203, 215-227. 1932; 36: 377-389. 1934; 39: 210- 

 231. 1937; 41: 1-19, 43-77. 1939.] 



The following key is adapted from Svenson's monographic studies of the 

 genus. Svenson has checked the determination of all of my specimens. 



Scales of mature spikelets persistent; spikelets scarcely thicker than the culms. 

 Fruiting culms more than 2 mm in diameter; nerves of scales faint. 



Culms terete, with conspicuous cross-partitions 1. E. equisetoides. 



Culms quadrangular, without cross-partitions. . .2. E. quadrangulata var. crassior. 



Fruiting culms not more than 2 mm in diameter; nerves of scales distinct 



3. E. Robbinsii. 



Scales of mature spikes deciduous; spikelets thicker than the culms. 

 Styles 2-cleft. 



Upper sheaths loose, with white, scarious tips 4. E. olivacea. 



Upper sheaths close and firm, not scarious at the tips. 

 Annual, with fibrous roots. 



Tubercle (style base) often depressed or saucer-shaped 5. E. geniculata. 



Tubercle more or less conical. 



Width of tubercle less than two thirds that of the achene. 



Achenes smooth; tubercle about half as wide as the achene.. .6. E. ovata. 



Achenes pitted; tubercle about a fourth as wide as the achene 



7. E. intermedia. 



Width of tubercle nearly or quite equal to that of the achene. 



Tubercle deltoid, a third to nearly a half as high as the body of the 

 achene; bristles much exceeding the achene. 



Spikelets ovoid-cylindric 8. E. obtusa. 



Spikelets ellipsoid 8a. E. obtusa var. ellipsoidalis. 



Tubercle very low, not more than a fourth as high as the body of the 

 achene; summit of achene appearing truncate; bristles equaling the 

 achene or rudimentary. 



Bristles about equaling the achene 9. E. Engelmanni. 



Bristles absent or rudimentary 9a. E. Engelmanni f. detonsa. 



