ONAGRACEAE OF OHIO. 
Rose Gormley. 
Onagraceae. Evening-primrose Family. 
Annual or perennial herbs, rarely shrubs, with alternate or 
opposite leaves without stipules, and with axillary, spicate or 
racemose, bisporangiate, epigynous flowers often with an hypan- 
thium; sepals 2-6 (usually 4) rarely none; stamens as many or 
twice as many as the petals; ovularly with 1-6 cavities, styles 
united; ovules indefinite, usually anatropous; fruit, a capsule or 
small nut; seeds, small; endosperm little or none; embryo straight. 
Synopsis. 
I. Fruit a many-seeded capsule opening by valves or pores; cavities 6-4. 
A. Floral parts not on an hypanthium. 
1. Seeds naked; calyx persistent. 
a. Leaves alternate. Ludwigia (1). 
b. Leaves opposite; petals none or very small; stems 
creeping or floating. Isnardia (2). 
2. Seeds with a tuft of silky hairs; calyx deciduous. 
Chamaenerion (3). 
B. Floral parts on a prominent epigynous hypanthium. 
1. .Seeds with a tuft of silky hairs. Epilobium (4). 
2. Seeds naked or sometimes tuberculate. 
a. Stamens equal in length. 
1. Ovules and seeds horizontal and prismatic¬ 
angled. Oenothera (5). 
2. Ovules and seeds ascending, not angled. 
Raimannia (6). 
b. Stamens unequal in length, one set longer. 
1. Ovules and seeds many. Kneiffia (7). 
Hartmann ia (8). 
2. Ovules and seeds few. Lavauxia (9). 
II. Fruit indehiscent; cavities 4-1. 
A. Floral whorls 4-parted. Gaura (10). 
B. Floral whorls 2-parted. Circaea (11). 
Key. 
1. Floral whorls with 4 or more parts. 2. 
1. Foral whorls 2 parted. Circaea (11). 
2. Without an hypanthium. 3. 
2. Floral parts on a prominent hypanthium. 5. 
3. Leaves alternate. 4. 
3. Leaves opposite; stamens 4; flowers axillary. Isnardia (2). 
4. Fowers in terminal racemes, purple or white. Chamaenerion (3). 
4. Flowers axillary in ours, yellow or green. Ludwigia (1). 
5. Plants acaulescent, stamens unequal in length; flowers in our species 
white or pink. Lavauxia (9). 
5. Plants caulescent. 6. 
6. Flowers yellow. 7. 
6. Flowers white, pink or red. 9. 
7. Stamens all of the same length; flowers nocturnal. 8. 
7. Alternate stamens longer; flowers diurnal. Kneiffia (7). 
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