1	"Fruit indehiscent, short"	2
1	"Fruit dehiscent, generally elongate"	5
2	"Fruit +- linear; stalk-like base 2--8 mm, slender"	"Oenothera sinuosa"
2	"Fruit fusiform to ovoid; stalk-like base 0--3 mm, thick if present"	3
3	"Annual; sepals 2--3.5 mm, barely opening; stalk-like base of fruit 0"	"Oenothera curtiflora"
3	"Perennial herb; sepals 5--14 mm, widely opening; stalk-like base of fruit short, thick"	4
4	"Fruit base > 1/2 diam of widest part, fruit becoming wider +- gradually; caudex woody, branched below ground"	"Oenothera suffrutescens"
4	"Fruit base +- 1/4 diam of widest part, fruit with a conspicuous, abrupt bulge near middle; rhizomed"	"Oenothera xenogaura"
5	"Fruit winged, angled or ribbed, basal part sterile"	6
5	"Fruit not winged, often angled or tubercled, fertile throughout"	8
6	"Petals yellow; fruit winged in distal 2/3, not narrower toward base"	"Oenothera flava"
6	"Petals white, rose, or rose-purple; basal part of fruit narrower, sterile; seeds clustered"	7
7	"Hypanthium 4--8 mm; petals 5--10 mm; fruit base tapered"	"Oenothera rosea"
7	"Hypanthium 10--23 mm; petals 25--40 mm; fruit base cylindric"	"Oenothera speciosa"
8	"Fruit tubercled; petals white"	9
8	"Fruit not tubercled; petals yellow or white"	11
9	"Annual; hypanthium 20--37(47) mm; sepals 4.5--12 mm; petals 6.5--20(25) mm"	"Oenothera cavernae"
9	"Perennial herb; hypanthium 30--165 mm; sepals 16--50 mm, tips in bud not free; petals 16--56 mm"	10
10	"Fruit 10--34 mm, lanceolate to elliptic-ovate, generally S-shaped, stalk-like base 0--1 mm; petals fading rose to purple; margin of seed-cavity lobed"	"Oenothera cespitosa subsp. crinita"
10	"Fruit 25--68 mm, cylindric, +- straight, stalk-like base 0--55 mm; petals fading lavender to pink; margin of seed-cavity entire"	"Oenothera cespitosa subsp. marginata"
11	"Petals white; stem peeling; bud nodding; seeds in 1 row per chamber"	12
11	"Petals yellow; stem generally not peeling; buds generally erect(nodding in <i>Oenothera pubescens</i>); seeds generally in 2 rows per chamber"	18
12	"Perennial herb; new shoots generally from lateral roots; free sepal tips in bud 0 or < 1 mm"	13
12	"Annual or perennial herb; new shoots from lateral roots 0; free sepal tips in bud 0--1.2 mm (pl annual or short-lived perennial herb) or 1--9 mm (pl perennial herb)"	15
13	"Stem hairs dense, short, appressed and long, spreading, wavy; roots fleshy; new rosettes at stem tips"	"Oenothera californica subsp. eurekensis"
13	"Stem hairs 0 (to dense, short, appressed and long, spreading); roots not fleshy; new rosettes not forming at stem tips"	14
14	"Cauline leaves generally +- pinnately lobed; plant +- gray-green"	"Oenothera californica subsp. avita"
14	"Cauline leaves +- entire to deeply wavy-dentate; plant green to slightly +- gray"	"Oenothera californica subsp. californica"
15	"Perennial herb, gray-green; free sepal tips in bud 1--9 mm"	"Oenothera deltoides subsp. howellii"
15	"Annual or short-lived perennial herb, green; free sepal tips in bud 0--1 mm"	16
16	"Distal leaves pinnately lobed; stem generally < 1 dm; petals 15--25(30) mm"	"Oenothera deltoides subsp. piperi"
16	"Distal leaves +- entire to +- dentate, rarely pinnately lobed; stem generally 2--10 dm; petals 15--43 mm"	17
17	"Spreading hairs +- 2 mm distally; fruit base 3--5 mm wide"	"Oenothera deltoides subsp. cognata"
17	"Spreading hairs 1--1.5 mm distally; fruit base 2--3 mm wide"	"Oenothera deltoides subsp. deltoides"
18	"Fruit lanceolate to ovate; seed 2.4--3.5 mm, +- wrinkled"	19
18	"Fruit +- cylindric (sometimes slightly wider toward tip); seed 1--2 mm, pitted"	21
19	"Petals fading deep salmon-red; fruit twisted; 1 side of seed with 2 small ridges; c&s SNH"	"Oenothera xylocarpa"
19	"Petals fading red-purple to orange; fruit not twisted; 1 side of seed with thick, U-shaped area surrounding a groove; D"	20
20	"Petals (22)29--40 mm; leaf gray-green"	"Oenothera primiveris subsp. bufonis"
20	"Petals 6--25(28) mm; leaf generally green"	"Oenothera primiveris subsp. primiveris"
21	"Stem decumbent to erect; annual or perennial herb (except <i>Oenothera stricta</i>, <i>Oenothera pubescens</i> biennial); flowers few, in distal axils"	22
21	"Stem erect; biennial; flowers in generally dense spikes; seeds angled, irregularly pitted"	24
22	"Bud erect; petal base generally with a red spot"	"Oenothera stricta subsp. stricta"
22	"Bud nodding or curved upward; petal base unspotted"	23
23	"Bud curved upward; sepal free tips in bud 0.3--3 mm"	"Oenothera laciniata"
23	"Bud nodding; sepal free tips in bud 0.1--1 mm"	"Oenothera pubescens"
24	"Hypanthium 60--135 mm"	"Oenothera longissima"
24	"Hypanthium 20--55 mm"	25
25	"Petals 25--52 mm; stigma well exceeding anthers; pollen +- all fertile or +- 50% sterile (sterile grains small and shriveled at 10&times;)"	26
25	"Petals 7--25(30) mm; stigma +- not exceeding anthers; pollen +- 50% sterile"	28
26	"Leaf crinkled; seeds and pollen +- 50% sterile"	"Oenothera glazioviana"
26	"Leaf +- flat, +- not crinkled; seeds and pollen +- all fertile"	27
27	"Sepals green or red-flushed; red blister-like hair bases on sepals +- 0; anthers 8--15 mm"	"Oenothera elata subsp. hirsutissima"
27	"Sepals red-flushed; red blister-like hair bases on sepals conspicuous; anthers 12--23 mm"	"Oenothera elata subsp. hookeri"
28	"Petals 13--23 mm, generally < sepals; generally coastal"	"Oenothera wolfii"
28	"Petals 7--25(30) mm, +- = sepals; generally not near coast"	29
29	"Spike dense (internodes in fruit < fruit); longest hairs generally without red blister-like bases; petals 10--25(30) mm; sepals green or +- yellow (+- red)"	"Oenothera biennis"
29	"Spike +- open (internodes in fruit generally > fruit); longest hairs generally with red blister-like bases; petals 7--20 mm; sepals often marked +- red"	"Oenothera villosa subsp. strigosa"