ONAGRAC'EAE, the Evening Primrose Family 



Herbs with opposite or alternate simple leaves and regular flow- 

 ers; sepals and petals each 4 (or 2 in one genus), stamens 8 (or 2 

 in one genus), attached to the summit or inside of a tubular receptacle; 

 ovary 2 4-celled, inferior. 



la. Aquatic plant of shallow water or muddy ground, with prostrate 

 stem (flowers minute, axillary; petals small or none, summer) 



Water Purslane, Ludvigia palustris* 

 Ib. Land plants with erect or ascending stems 2. 



2a. Petals minute, greenish (3 8 dm. high; late summer) 



False Loosestrife, Ludvigia polycarpa. 

 2b. Petals yellow 3. 



2c. Petals white, pink, purple, or red 9. 



3a. Sepals borne at the summit of the ovary (5 10 dm. high; sum- 

 mer) False Loosestrife, Ludvigia alternifolia, 

 3b. Sepals borne at the summit of the slender tubular receptacle, 

 which is prolonged beyond the ovary 4. 



4a. Stamens all equal in length (Evening Primrose) 5. 



4b. The alternate stamens longer (3 8 dm. high; summer) 



(Sundrops) 8. 



5a. Leaves deeply dentate or pinnatifid (2 5 dm. high; early sum- 

 mer) Evening Primrose, Oenothera laciniata. 

 5b. Leaves entire or undulate or finely toothed (5 12 dm. high; sum- 

 mer) 6. 

 6a. Hairs on the stem with broad reddish bases 



Evening Primrose, Oenothera muricata. 

 6b. Hairs on the stem none, or without swollen bases 7. 



7a. Stem and foliage glabrous, or with sparse spreading hairs 



Evening Primrose, Oenothera biennis, 

 7b. Stem and foliage densely but closely appressed-pubescent 



Evening Primrose, Oenothera rhoinbipetala. 



8a. Petals 5 10 mm. long Sundrops, Oenothera pumila. 



8b. Petals 14 mm. long or more Sundrops, Oenothera fruticosa. 



9a. Petals 2, reverse heart-shape, stamens 2 (flowers small, white, 



summer) (Enchanter's Nightshade) 10. 

 9b. Petals 4; stamens 4 or 8 12. 



lOa. Leaves rounded at the base, denticulate (3 8 dm. high; 

 fruit prickly) Enchanter's Nightshade, Circaea lutetiana. 



lOb. Leaves cordate at the base 11. 

 lla. Fruit 2-celled, bristly (24 dm. high) 



Enchanter's Nightshade, Circaea intermedia. 



lib. Fruit 1-celled, with soft hairs (delicate plant 2 dm. high, or 

 less) Enchanter's Nightshade, Circaea alpina. 



12a. Petals entire (summer) 13. 



.12b. Petals notched at the end (flowers white or pinkish, less 

 than 1 cm. broad, in summer) (Willow Herb) 15. 



