Rhynchospora alba
 
White Beak-Rush

Bristles, Filaments, and Achene

Greenbush Bog, 20 km West of Hudson Bay, SK on Highway #3
28-July-2016

According to the Flora of North America, there are 10 to 12 bristles.  This specimen appears to have 13.  Note the two filaments and the two stigmas.

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Alba: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan by V. L. Harms, A. L. Leighton, and M. A. Vetter leading to this species. The answers are in the order you would normally work through the key. 
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Spikelet clusters usually top-shaped (turbinate) to hemispheric with spikelets pale (pale brown or stramineous to sometimes whitish to light reddish brown); bracts subtending the lowest inflorescence clusters seldom exceeding terminal spikelet clusters; bristles 10-12, usually +/- setulose at base.  NOT [Spikelet clusters usually ellipsoidal to turbinate with spikelets brown to reddish brown; bracts subtending the lowest inflorescence clusters usually exceeding terminal spikelet clusters; bristles 5 - 6, not setulose at base.]

 

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Rhynchospora: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan by V. L. Harms, A. L. Leighton, and M. A. Vetter leading to this genus. The answers are in the order you would normally work through the key. 
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Flowers and achenes naked in the axils of scales, not enclosed in a sac; flowers usually perfect (sometimes some flowers imperfect in Cyperus, Rhynchospora and Cladium).  NOT [Flowers and achenes enclosed in a sac (perigynium) borne in the axils of scales; flowers imperfect.]

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Perianth bristles absent or up to 6 per flower; if more than 6, then only somewhat longer than the achenes.  NOT [Perianth bristles usually more than 10 per flower, much longer than the achenes, conspicuously elongated to over 10 mm long in fruit stage and usually obscuring most scales in spikelets.]

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Inflorescence not a solitary, terminal spike; if solitary, terminal and spike-like, then inflorescence +/- terete.  NOT [Inflorescence a compressed, solitary, terminal spike bearing few-flowered spikelets attached in 2 rows.]

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Inflorescence usually with > 1 spikelet; if only 1 spikelet present, then inflorescence bract usually 10 - 200 mm long (but as short as 7 mm in Schoenoplectus subterminalis) and achenes 2 - 3.5 mm long.  NOT [Inflorescence a solitary terminal spikelet; inflorescence bracts absent or up to 8 mm long and only slightly longer than the spikelet; achenes usually <= 2 mm long (up to 2.3 mm in Eleocharis quinqueflora).]

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Achenes with a narrowly triangular tubercle.  NOT [Achenes lacking a tubercle but sometimes beaked.]

 

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Cyperaceae: Answers to key questions in Budd's Flora leading to this family. 
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plants not aquatic, or if growing in water, most of the plant emersed; NOT [plants aquatic, floating or submerged, with floating leaves or emersed inflorescence]

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culms usually solid; NOT culms usually hollow]

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leaves three-ranked; NOT [leaves two-ranked]

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inflorescence NOT [a dense, single, cylindrical spike 8-15 cm long, 1-2.5 cm thick],  if a single spike, less than 1 cm thick

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flowers not in globular heads; NOT [flowers in globular heads, the upper ones staminate, the lower ones pistillate]

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flowers solitary in the axil of a single bract (scale); NOT [flowers enclosed in two-ranked bracts with the lowest (glumes) empty]

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perianth absent or inconspicuous, not in two whorls; NOT [perianth present, conspicuous, in two whorls of 3 segments each, often brightly colored]

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perianth reduced to bristles or scales or lacking; NOT [perianth reduced to minute lodicules or lacking]