We have two recognized variants. 



Van occidentale (Trel.) C. L. Hitchc. is glandular-pubescent in the inflorescence. 

 Var. Parishii (Trel.) C. L. Hitchc. has nonglandular somewhat appressed hairs. 



3. Oenothera L. Evening Primrose 



Herbs, sometimes woody near the base, with alternate entire to pinnatifid leaves; 

 stipules absent; flowers actinomorphic, 4-merous, borne in the axils of upper leaves 

 or in a more or less distinct inflorescence, opening either near sunset or near sun- 

 rise; hypanthium well-developed; sepals not persistent in fruit; petals yellow or 

 white to rose-purple; stamens 8; stigma deeply 4-lobed; fruit a loculicidally dehis- 

 cent or nutlike indehiscent capsule; seeds lacking a coma. 



About 80 species of the temperate regions of North America and South America, 

 widely introduced elsewhere. 



Oenothera sessilis (Penn.) Munz, distinguished by its yellow flowers and linear- 

 clavate subsessile to shortly stipitate capsules, was last collected in marshy place 

 near Galveston, Texas, more than 100 years ago. It is also found in Louisiana. 



1. Capsule clavate, the lower part narrowed and stipelike; seeds clustered, not in 

 definite rows (2) 



1. Capsule ovoid to cylindric; seeds usually in definite rows (5) 



2(1). Petals rose-color; flowers opening near sunrise (3) 



2. Petals white, fading pinkish; flowers opening near sunset (4) 



3(2). Stigma usually elevated above the anthers; hypanthium 10-30 mm. long; 

 petals 20—35 mm. long 1. O. tetraptera. 



3. Stigma surrounded by the anthers; hypanthium (5-) 20 mm. long; petals 



10-20 mm. long 2. O. Kunthiana. 



4(2). Hypanthium 15-21 mm. long; petals 12-21 mm. long 3. O. texensis. 



4. Hypanthium 4-8 mm. long; petals 4.5-12 mm. long 4. O. rosea. 



5(1). Capsule ovoid-pyramidal or oblong-ovoid, commonly indehiscent; low rhi- 

 zomatous or acaulescent herbs (6) 



5. Capsule subcylindrical, readily dehiscent at maturity (at least at the apex) (7) 



6(5). Acaulescent herb; leaves rosulate, more than 2 cm. long; hypanthium much 

 more than 20 mm. long 5. O. flava. 



6. Low bushy plant; leaves cauline, less than 1.5 cm. long; hypanthium 5-15 



mm. long 6. O. canescens. 



1{S). Seeds ascending, not sharply angled; capsule oblong-fusiform to subclavate 



7. O. rhombipetala. 



1. Seeds horizontal, sharply angled; capsule gradually tapered upward (8) 



8(7). Petals 1-2 cm. long; styles mostly 0.3-1.7 mm. long 8. O. biennis. 



8. Petals 2-5 cm. long; styles 20-60 mm. long (9) 



9(8). Hypanthium 25-45 mm. long 9. O. Hookeri. 



9. Hypanthium 60-120 mm. long (10) 



10(9). Distribution in Oklahoma and Texas 10. O. Jamesii. 



10. Distribution in Arizona II. O. longissima. 



1. Oenothera tetraptera Cav. 



Well-branched strigulose to hirsute annual to 4 dm. tall; leaves sinuate to sinuate- 

 pinnatifid, the upper ones subentire, lanceolate to oblanceolate or occasionally nar- 

 rowly elliptic, 1-9 cm. long, (2-) 10-25 mm. wide, the petiole 2-20 mm. long; 

 flowers opening near sunset; mature buds erect; hypanthium 1-3 cm. long; sepals 

 2-4 cm. long, with free tips to 3 mm. long; petals white, fading pink, 2-3.5 cm. 



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