Hooker's Evening Primrose
Oenothera elata
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Hairy Evening Primrose
Oenothera elata ssp. hirsutissima
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Hooker's Evening Primrose
Oenothera elata ssp. hookeri
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Yellow Evening Primrose
Oenothera flava
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Long-stem Evening-primrose
Oenothera longissima
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Desert Evening Primrose
Oenothera primiveris
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Desert Evening Primrose
Oenothera primiveris ssp. primiveris
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South American Evening Primrose
Oenothera pubescens
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Wild Honeysuckle
Oenothera suffrutescens
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Hairy Evening Primrose
Oenothera villosa
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Hairy Evening Primrose
Oenothera villosa ssp. strigosa
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Wolf's Evening-primrose
Oenothera wolfii
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Woodyfruit Evening Primrose
Oenothera xylocarpa
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Lineleaf Whitepuff
Oligomeris linifolia
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Desert Ironwood
Olneya tesota
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Douglas' Grasswidow
Olsynium douglasii
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Purple Eyed Grass
Olsynium douglasii var. douglasii
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California Adder's-tongue
Ophioglossum californicum
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Northern Adder's-tongue
Ophioglossum pusillum
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Baby Rita Prickly Pear Cactus
Opuntia 'Baby Rita'
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Beavertail Pricklypear
Opuntia basilaris
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Beavertail Pricklypear
Opuntia basilaris var. basilaris
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Short-joint Beavertail
Opuntia basilaris var. brachyclada
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Bakersfield Cactus
Opuntia basilaris var. treleasei
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Pancake Prickly-pear
Opuntia chlorotica
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Tulip Pricklypear
Opuntia engelmannii
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Engelmann Prickly-pear
Opuntia engelmannii var. engelmannii
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Pigmy Tuna
Opuntia fragilis
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Coast Prickly Pear
Opuntia littoralis
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Opuntia occidentalis
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Chaparral Pricklypear
Opuntia oricola
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Tulip Pricklypear
Opuntia phaeacantha
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Plains Pricklypear
Opuntia polyacantha
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Grizzlybear Pricklypear
Opuntia polyacantha var. erinacea
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Porcupine Prickly-pear
Opuntia polyacantha var. hystricina
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Vasey's Prickly Pear
Opuntia vaseyi
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California Orcutt Grass
Orcuttia californica
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San Joaquin Valley Orcutt Grass
Orcuttia inaequalis
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Hairy Orcutt Grass
Orcuttia pilosa
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Slender Orcutt Grass
Orcuttia tenuis
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Sacramento Orcutt Grass
Orcuttia viscida
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Bow-nut Cryptantha
Oreocarya abortiva
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Yellow-flowered Cryptantha
Oreocarya confertiflora
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Subalpine Cryptantha
Oreocarya crymophila
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Yellow-eyed Cryptantha
Oreocarya flavoculata
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Cocks-comb Cat's-eye
Oreocarya glomerata
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White Mountains Cryptantha
Oreocarya hoffmannii
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Low Cryptantha
Oreocarya humilis ssp. humilis
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Sierra Cryptantha
Oreocarya nubigena
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Bristlecone Cryptantha
Oreocarya roosiorum
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Schoolcraft's Cryptantha
Oreocarya schoolcraftii
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Crater Lake Cryptantha
Oreocarya subretusa
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New York Mountains Cryptantha
Oreocarya tumulosa
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Virgin River Cryptantha
Oreocarya virginensis
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Oreonana Clementis
Oreonana clementis
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Purple Mountain-parsley
Oreonana purpurascens
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Woolly Mountain-parsley
Oreonana vestita
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Tundra Aster
Oreostemma alpigenum
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Alpine Aster
Oreostemma alpigenum var. andersonii
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Tall Alpine-aster
Oreostemma elatum