CYPERACEAE 
angles and appearing turgid. Base of the style presistent on the summit 
forming a tubercle. 
Spikelet scarcely 
SPIKE RUSH. 
or not at all thicker than the scape: scales mostly leathery. 
Bristles 6, as long as the achene or shorter: scapes relatively stout. 
Scapes tere 
te, at least above: achenes not cancellate. 
Achenes transversely ridged : scapes nodose-septate. 
Achenes copiously pitted : scapes continuous. 
Scapes sharply 4-angled: achenes cancellate. 
Bristles 7, longer than the achene: scapes relatively slender. 
Spikelet 6-8-flowered: achenes about 2 mm. long, deeply pitted : scapes 3- 
angled. 
Spikelet 12-20-flowered: achenes about 1 mm. long, faintly pitted: scapes 
terete. 
Spikelet manifestly thicker than the scape: scales mostly membranous. 
Style-branches or stigmas 2: achene lenticular or biconvex. 
Upper sheath scarious, hyaline: plants perennial by slender rootstocks. 
Achenes 
Seales pale green or rarely white: perianth-bristles longer than the 
about 0.5 mm. long. 
achene. 
Scales brown: perianth-bristles shorter than the achene. 
Achenes 
about 1 mm. long. 
Scapes 2-10 em. long: perianth-bristles longer than the achene. 
Seapes 10-35 em. long: perianth-bristles as long as the achene. 
Upper sheath truncate, oblique or toothed, not scarious. 
Annuals with fibrous roots. 
Scapes capillary: spikelets with 1-4 achenes. 
Seapes slender: spikelets with several to many achenes. 
Ac 
Ac 
henes black. 
eee 2-4, pale: achenes 0.5 mm. long: scapes 2-9 cm. 
tall. 
pas op tA oat 5-8, brown: achenes 1 mm, long: scapes 5-25 
em. tall. 
henes pale brown to white. 
Scapes filiform : achene white. 
Seapes slender: achenes pale brown. 
Scales of the spikelets obtuse. 
Perianth-bristles longer than the achene: spikelets ovoid. 
Perianth-bristles not longer than the achene, often short or 
wanting: spikelets cylindric. 
Scales of the spikelets acute. 
Perennials with horizontal rootstocks. 
Scape 
s nodose-septate. 
Scapes continuous. 
Scales pale green or straw-colored : scape relatively stout. 
Scales brown or dark green: scapes slender or filiform. 
Achenes 1.5 mm. long: tubercle conic. 
Achenes 1 mm. long or less: tubercle depressed. 
Style-branches or stigmas 3: achene 3-angledior turgid. 
Achene cancellate. 
Achene longitudinally ribbed. 
Achene not longitudinally ribbed. 
Scapes filiform: spikelets with 1-4 achenes. 
Scapes slender: spikelets with many achenes. 
Spikelets linear-oblong, often proliferous. 
Spi 
kelets ovoid to conic-ovoid, not proliferous. 
Tubercle conic, smaller than the achene. 
Tubercle cap-like, as large as the achene or larger. 
Achene smooth. papillose. or irregularly ridged-reticulated. 
Seapes capillary or filiform. 
Spikelets terete or nearly so, 6-2- flowered. 
Spikelets oblong, 3-6 mm. long. 
Spikelets ovoid, 2-3 mm. long. 
Spikelets flattened. 2-6-flowered, often proliferous. 
Achene obovoid : tubercle deltoid or Dd rris 
Achene oblong: tubercle abruptly subu 
slender or stout. 
Sea 
ate-tipped. 
bercle plainly distinguishable from the achene. 
Spikelets ovoid to oblong: achene not constricted at the neck. 
Achenes smooth. 
Tubercle flat, covering the top of the black achene. 
Tubercle ovoid-conic, acute, contracted at the base. 
Achenes papillose or irregularly ridged-reticulated. 
Achenes with the 3 angles ribbed. 
Achenes obtusely 3-angled. 
Scapes slender to nearly filiform : scales obtuse. 
Bristles 2-4, shorter than the achene: achene strongly 
pillose to reticulated. 
Bristles 6, the longer as long as the achene: achene 
faintly reticulated. 
Sea flattened : scales acute. 
pes 
Spikelets linear-cylindric : achene constricted at the neck. 
Tubercle long-conic, scarcely distinguishable from the achene. 
1. Eleocharis interstíncta (Vahl) R. & S. Perennial by stout rootstocks. 
eur 
eom 
30. 
31. 
32. 
33. 
34. 
35. 
181 
of the achene, 
. E. interstincta. 
E. cellulosa. 
E. mutata. 
E. Robbinsii. 
. E. elongata. 
. E. ochreata. 
. E. praticola. 
. E. olivacea. 
. E. maculosa. 
E. capillacea. 
. E. atropurpurea. 
. E. capitata. 
. E. bicolor. 
. E. obtusa. 
E. Engelmannii. 
. E. lanceolata. 
. E. nodulosa. 
. E. macrostachya. 
. E. glaucescens. 
E. Ravenelii. 
. E. acicularis. 
. E. Chaetaria. 
. E. vivipara. 
. E. tortilis. 
. E. tuberculosa. 
. E. Torreyana. 
. E. microcarpa. 
h x gron ifera. 
aldwinii. 
E. melanocarpa. 
E. albida. 
E. tricostata. 
E. tenuis. 
E. arenicola. 
E. acuminata. 
36. E. cylindrica. 
37. E. 
. rostellata. 
Scapes 
terete, hollow, nodose-septate, 4-9 dm. tall, the sterile ones sharp-pointed : sheaths mem- 
